Critical Reasoning

For the last five years, the XYZ Courier Company has made regular delivery trips between Town A and Town B. The average time taken by the company's drivers to drive the round trip between the two towns, excluding the time taken for loading, unloading, and delivery, over that period has been 80 minutes. John, a driver for XYZ, needs to make a personal trip between the two towns; he figures that he should allow approximately 80 minutes for the round trip.

Which of the following, if true, does not call John's conclusion into question?

A)The route between Town A and Town B has been plagued by increasing congestion over the last five years, as the area's population has doubled during that time.

B)Most of XYZ's courier vehicles are heavy trucks, for which speed limits are lower than for passenger vehicles.

C)Many of the packages carried by XYZ between Town A and Town B are large, high-security packages, for which the processes of loading, unloading, and delivery can take up to half the length of the trip itself.

D)John will make his personal trip at an hour when XYZ does not make delivery trips.

E)Before a freeway was built between Town A and Town B two years ago, the only routes between the two towns were state highways with multiple traffic lights and reduced-speed downtown zones.

OA: C

[spoiler]How answer A would weaken the conclusion??[/spoiler]

joealam1 wrote:For the last five years, the XYZ Courier Company has made regular delivery trips between Town A and Town B. The average time taken by the company's drivers to drive the round trip between the two towns, excluding the time taken for loading, unloading, and delivery, over that period has been 80 minutes. John, a driver for XYZ, needs to make a personal trip between the two towns; he figures that he should allow approximately 80 minutes for the round trip.

Which of the following, if true, does not call John's conclusion into question?

Conclusion: John should allow approximately 80 minutes for the round trip.
Eliminate the four answer choices that weaken John's conclusion.

A) The route between Town A and Town B has been plagued by increasing congestion over the last five years, as the area's population has doubled during that time.
Implication:
Since congestion has been increasing, the CURRENT time required for the trip is probably MORE than the AVERAGE time over the past five years.
Thus, John will probably need MORE than 80 minutes for his trip.
Eliminate A.

B) Most of XYZ's courier vehicles are heavy trucks, for which speed limits are lower than for passenger vehicles.
Since his personal vehicle is almost certainly not a heavy truck, John can drive at a higher speed and thus will need LESS than 80 minutes for his trip.
Eliminate B.

C) Many of the packages carried by XYZ between Town A and Town B are large, high-security packages, for which the processes of loading, unloading, and delivery can take up to half the length of the trip itself.
Since the given time of 80 minutes excludes the time taken for loading, unloading, and delivery, the information in C is irrelevant.

D) John will make his personal trip at an hour when XYZ does not make delivery trips.
Since the 80 minutes required by XYZ trucks might not apply to the time of day at which he will make his trip, John might need MORE or LESS than 80 minutes for his journey.
Eliminate D.

E) Before a freeway was built between Town A and Town B two years ago, the only routes between the two towns were state highways with multiple traffic lights and reduced-speed downtown zones.
Implication:
The extra routes might enable to John to make his trip in LESS than 80 minutes.
Eliminate E.

The correct answer is C.