Earthworm

krishnapavan wrote:Two types of earthworm, one black and one red-brown, inhabit the woods near the town of Millerton. Because the red-brown worm's coloring affords it better camouflage from predatory birds, its population in 1980 was approximately five times that of the black worm. In 1990, a factory was built in Millerton and emissions from the factory blackened much of the woods. The population of black earthworms is now almost equal to that of the red-brown earthworm, a result, say local ecologists, solely stemming from the blackening of the woods.

Which of the following, if true, would most strengthen the conclusion of the local ecologists?

A. The number of red-brown earthworms in the Millerton woods has steadily dropped since the factory began operations.
B.The birds that prey on earthworms prefer black worms to red-brown worms.
C. Climate conditions since 1990 have been more favorable to the survival of the red-brown worm than to the black worm.
D.The average life span of the earthworms has remained the same since the factory began operations.
E. Since the factory took steps to reduce emissions six months ago, there has been a slight increase
in the earthworm population.

IMO A

krishnapavan wrote:Two types of earthworm, one black and one red-brown, inhabit the woods near the town of Millerton. Because the red-brown worm's coloring affords it better camouflage from predatory birds, its population in 1980 was approximately five times that of the black worm. In 1990, a factory was built in Millerton and emissions from the factory blackened much of the woods. The population of black earthworms is now almost equal to that of the red-brown earthworm, a result, say local ecologists, solely stemming from the blackening of the woods.

Which of the following, if true, would most strengthen the conclusion of the local ecologists?

A. The number of red-brown earthworms in the Millerton woods has steadily dropped since the factory began operations.
B.The birds that prey on earthworms prefer black worms to red-brown worms.
C. Climate conditions since 1990 have been more favorable to the survival of the red-brown worm than to the black worm.
D.The average life span of the earthworms has remained the same since the factory began operations.
E. Since the factory took steps to reduce emissions six months ago, there has been a slight increase
in the earthworm population.

IMO D
The reasoning : Goal here is to prove that the factory was the sole factor in deciding the numbers of the brown and black worms. For this to be true both worms should have all other factors constant (including lifespan). If brown had a much shorter life span, then we cannot prove that the factory had a role to play in it.

Please let me know the OA.

OA is C

krishnapavan wrote:Two types of earthworm, one black and one red-brown, inhabit the woods near the town of Millerton. Because the red-brown worm's coloring affords it better camouflage from predatory birds, its population in 1980 was approximately five times that of the black worm. In 1990, a factory was built in Millerton and emissions from the factory blackened much of the woods. The population of black earthworms is now almost equal to that of the red-brown earthworm, a result, say local ecologists, solely stemming from the blackening of the woods.

Which of the following, if true, would most strengthen the conclusion of the local ecologists?

A. The number of red-brown earthworms in the Millerton woods has steadily dropped since the factory began operations.
B.The birds that prey on earthworms prefer black worms to red-brown worms.
C. Climate conditions since 1990 have been more favorable to the survival of the red-brown worm than to the black worm.
D.The average life span of the earthworms has remained the same since the factory began operations.
E. Since the factory took steps to reduce emissions six months ago, there has been a slight increase
in the earthworm population.

I think the answer should be C

It rules out the possibility that the climate conditions may have affected the population of the redworm and strengthens the premise that the color change is the sole reason why birds eat them.

Hope that makes sense.

imo D

C is good: it suggests that, all things considered, the red-brown worm should be doing BETTER than the black worm ... but this clearly isn't happening! Hence the black worm must be doing better, supporting our contention that the blackened woods are a better environment for the black worm.

krishnapavan wrote:Two types of earthworm, one black and one red-brown, inhabit the woods near the town of Millerton. Because the red-brown worm's coloring affords it better camouflage from predatory birds, its population in 1980 was approximately five times that of the black worm. In 1990, a factory was built in Millerton and emissions from the factory blackened much of the woods. The population of black earthworms is now almost equal to that of the red-brown earthworm, a result, say local ecologists, solely stemming from the blackening of the woods.

Which of the following, if true, would most strengthen the conclusion of the local ecologists?

A. The number of red-brown earthworms in the Millerton woods has steadily dropped since the factory began operations.
B.The birds that prey on earthworms prefer black worms to red-brown worms.
C. Climate conditions since 1990 have been more favorable to the survival of the red-brown worm than to the black worm.
D.The average life span of the earthworms has remained the same since the factory began operations.
E. Since the factory took steps to reduce emissions six months ago, there has been a slight increase
in the earthworm population.

Can someone explain each and every option? Especially the difference between B and C!

tarunjohri wrote:Can someone explain each and every option? Especially the difference between B and C!

here are my two cents......a good question for GMAT.


Two types of earthworm, one black and one red-brown, inhabit the woods near the town of Millerton. Because the red-brown worm's coloring affords it better camouflage from predatory birds, its population in 1980 was approximately five times that of the black worm. In 1990, a factory was built in Millerton and emissions from the factory blackened much of the woods. The population of black earthworms is now almost equal to that of the red-brown earthworm, a result, say local ecologists, solely stemming from the blackening of the woods.

Which of the following, if true, would most strengthen the conclusion of the local ecologists?

A. The number of red-brown earthworms in the Millerton woods has steadily dropped since the factory began operations
B.The birds that prey on earthworms prefer black worms to red-brown worms. (If we assume this is true, then black worms population wont increase and become equal to that of reds. so this cant be true.)
C. Climate conditions since 1990 have been more favorable to the survival of the red-brown worm than to the black worm. (assuming this is true. Now, climate conditions have been favorable to reds, even then, blacks have become almost equal. That means, the blacks have grown at phenomenal rate despite climate condition being more favorable to reds.......that means something else has caused black worms to increase in no. ad that sth is blackening of woods..... statement C compeltes the story)
D.The average life span of the earthworms has remained the same since the factory began operations.
E. Since the factory took steps to reduce emissions six months ago, there has been a slight increase
in the earthworm population.

I am thinking in terms of B is that since the birds prefer the black worm and it has still been able to increase in numbers this means it has found some help externally which is in the form of the blackening of leaves because had it not been the blackening of the leaves it would have not been able to reach numbers close to that of the red worm...am i wrong in this line of thought??

Matt@VeritasPrep wrote:C is good: it suggests that, all things considered, the red-brown worm should be doing BETTER than the black worm ... but this clearly isn't happening! Hence the black worm must be doing better, supporting our contention that the blackened woods are a better environment for the black worm.

krishnapavan wrote:Two types of earthworm, one black and one red-brown, inhabit the woods near the town of Millerton. Because the red-brown worm's coloring affords it better camouflage from predatory birds, its population in 1980 was approximately five times that of the black worm. In 1990, a factory was built in Millerton and emissions from the factory blackened much of the woods. The population of black earthworms is now almost equal to that of the red-brown earthworm, a result, say local ecologists, solely stemming from the blackening of the woods.

Which of the following, if true, would most strengthen the conclusion of the local ecologists?

A. The number of red-brown earthworms in the Millerton woods has steadily dropped since the factory began operations.
B.The birds that prey on earthworms prefer black worms to red-brown worms.
C. Climate conditions since 1990 have been more favorable to the survival of the red-brown worm than to the black worm.
D.The average life span of the earthworms has remained the same since the factory began operations.
E. Since the factory took steps to reduce emissions six months ago, there has been a slight increase
in the earthworm population.

can someone tell me what is wrong with D?
Is it an assumption? And not strengthening the conclusion?