[求助]LSAT-2-4-5

5. A government agency publishes ratings of airlines, ranking highest the airlines that have the smallest proportion of late flights. The agency's purpose is to establish an objective measure of the relative efficiency of different airlines's personnel in meeting published flight schedules.

Which one of the following, if true, would tend to invalidate use of the ratings for the agency's purpose?

A. Travelers sometimes have no choice of airlines for a given trip at a given time.

B. Flights are often made late by bad weather conditions that affect some airlines more than others.

C. The flight schedules of all airlines allow extra time for flights that go into or out of very busy airports.

D. Airline personnel are aware that the government agency is monitoring all airline flights for lateness.

E. Flights are defined as "late" only if they arrive more thatn fifteen minutes past their scheduled arrival time, and a record is make of how much later than fifteen minutes they are.

正确答案是B选项，我选的是A选项。对于A选项，我认为，旅客只能选择某一特定的航班，这样就没有使用ratings的必要了呀，不也就是invalidate use了吗？对于B选项，我反而认为是个加强的选项，我的想法是：正是由于天气原因，使得不同航线的效率不同，所以有使用ratings的必要啊。还请大牛多多帮忙啊。

It is an objective way to rank their individual proportion of late flights by measuring the effeciency of different airlines' personnel.

The assumption made by the arguer is that the efficiency of different airlines' personnel is the only reason for late flights.