My answer is D.

please tell the correct answer.

Please tell the correct answer.

what is the OA, BTW,can anybody paarphrase this sentence:no two bacterial strains on Earth are different enough to have arisen on different planets

I think it is D please tell us the correct answer.

jamesk486 wrote:Mars (Fill in): It is theoretically possible that bacteria developed on Mars early in its history and that some were carried to Earth by a meteorite. However, strains of bacteria from different planets would probably have substantial differences in protein structure that would persist over time, and no two bacterial strains on Earth are different enough to have arisen on different planets. So______________________________________________.
(What would be the best option to complete the passage?)
A. Whether or not bacteria actually developed on Mars.
B. Its likely it is that Martian bacteria were transported from Earth.
C. Martian bacteria could have been carried to Earth by means other than meteorites.
D. All bacteria now on Earth could have arisen from transported Martian bacteria.
E. There could have been strains of bacteria that originated on Earth and later died out.

The passage tells us that something is possible. We want something that allows us to have options for either/or. A does not even fit the passage. B is leaning towards one side over another - eliminate. Choices C and E require you to assume certain properties of bacteria and their interactive dynamics - eliminate them. You are left with D, so choose D.

However, D is a good answer because it parallels the passage in allowing either/or outcome. It is easy to overlook the "probably" in the second sentence and take it as fact. Do not fall for this trap. All of the passage is one big probability. Choice D follows this pattern.

Could you please explain why E is wrong...
and as other people have mentioned , why is D correct....

Mars (Fill in): It is theoretically possible that bacteria developed on Mars early in its history and that some were carried to Earth by a meteorite. However, strains of bacteria from different planets would probably have substantial differences in protein structure that would persist over time, and no two bacterial strains on Earth are different enough to have arisen on different planets.

D. All bacteria now on Earth could have arisen from transported Martian bacteria.
E. There could have been strains of bacteria that originated on Earth and later died out.

Anon,

The passage talks about a possibility of there being bacteria from Mars, which could have been carried to Earth by a meteorite. Then, it says - again, it is a probability - that bacteria from two DIFFERENT planets would have differences in structure. The whole passage is about the potential relationship of events involving two planets.

Option E attempts to see how well you have grasped the issues discussed in the passage by leading you to conclude that there is a possibility that once there was bacteria that was different in structure from bacteria presently on Earth. However, it also says that this strain of bacteria originated "on Earth and later died out." We do not care about bacteria that originated on Earth. We care about bacteria that originated from Mars.

Option D, on the other hand, returns to the potential relationship between Mars and Earth, and in part infers that perhaps the bacteria on Mars is the same in protein structure as bacteria on Earth, which would lead us to conclude that there is, once again, potential for bacteria presently on Earth to be from Mars. However, this COULD be true. As I said above, you are looking for an answer that parallels the passage in its uncertainty as it relates to a potential answer to the whole "protein structure difference" issue, and at the same time covers the topic of the passage, namely, the relationship between two planets, etc, etc, etc.

I really hope this helps.

Hey Alex,

Thanks for the wonderful expln...makes sense now..

No problem. Glad I could help.

jamesk486 wrote:Mars (Fill in): It is theoretically possible that bacteria developed on Mars early in its history and that some were carried to Earth by a meteorite. However, strains of bacteria from different planets would probably have substantial differences in protein structure that would persist over time, and no two bacterial strains on Earth are different enough to have arisen on different planets. So______________________________________________.
(What would be the best option to complete the passage?)
A. Whether or not bacteria actually developed on Mars.
B. Its likely it is that Martian bacteria were transported from Earth.
C. Martian bacteria could have been carried to Earth by means other than meteorites.
D. All bacteria now on Earth could have arisen from transported Martian bacteria.
E. There could have been strains of bacteria that originated on Earth and later died out.

Hi all,
I understand it like this:

Intro:
Theory> some kind of bacteria from Mars came to Earth carried by a metehorite

Opose:
Idea1> strains of bacteria from different planets have substantial differences in their protein structure
Idea2> no two bacterias on Earth have substantial differences, so they can not be from different planets

Conclusion:
So> even though it is theoretically possible, in the practice there is no choice of finding any strain of bacteria from Mars (or any other planet) on Earth.

I think it is letter E, even though it doesn´t convince me at all. Someone has the answer key for this question?

This is a main point question.

The conclusion is that all bacteria on earth originated on the same planet. The planet where it originated can be either earth or mars.

only D satisfies this conclusion.

i will go with D

i think option D is better