Since the early 1990s, many airliners have been equipped with telephon

­Since the early 1990s, many airliners have been equipped with telephones for passenger use. However, the telephones are expensive for passengers to use, and their use has declined, especially since cell phones have become more prevalent. Nevertheless, since airlines collect a portion of the charge for each call made without having to pay anything for the telephone equipment, which is owned and maintained by telephone companies, airlines clearly still benefit financially from the telephones.

The conclusion of the argument is the following:

airlines clearly still benefit financially from the telephones

The support for the conclusion is the following:

airlines collect a portion of the charge for each call made without having to pay anything for the telephone equipment

We see that the reasoning of the argument is basically that, since airlines generate revenue without having to pay for the telephone equipment used to generate the revenue, airlines benefit financially, meaning, basically., make a profit, by having the phones on their planes.

In drawing its conclusion, the argument depends on assuming which of the following?

The correct answer will state an assumption necessary for the evidence to support the conclusion.

A. The proportion of the charge for an in-flight telephone call that goes to the airline has not declined since the early 1990s.

To eliminate this choice, we need to notice that, even if the proportion of the charge for an in-flight telephone call that goes to the airline HAS declined since the early 1990s, airlines still collect a portion of the charge for each call made.

So, regardless of whether the proportion of the charge that goes to the airlines has declined, it still makes sense to conclude that airlines benefit financially from having the phones. After all, since the airlines don't pay anything for the telephone equipment, even if they don't get much revenue from the telephones, as long as they get some revenue, having the phones could benefit them financially.

Eliminate.

B. Despite the decline in usage, the in-flight telephones remain profitable for the telephone companies that own and maintain them.

The conclusion of the argument is that airlines benefit financially from the telephones.

This choice does not have to be true for that conclusion to follow from evidence. After all, even if the telephones do NOT remain profitable for telephone companies, they could still be a source of financial benefits for airlines.

Now, it's true that, if the telephones are not profitable for telephone companies, telephone companies may not continue to maintain phones in planes.

All the same, given that, as the passage indicates, the phones are currently in planes, they could be profitable for the airlines even if they are not for telephone companies.

So, the argument works even if this choice is not true.

Eliminate.

C. The telephone equipment does not weigh enough to make a material difference in the fuel consumption of airliners in which it is installed.

This choice is interesting.

After all, the conclusion is "airlines clearly still benefit financially from the telephones."

So, what if this choice is not true and the telephone equipment DOES weigh enough to make a material difference in fuel consumption? In that case, it's not clear that airlines benefit financially from the telephones. After all, in that case, it could be that the cost associated with the additional fuel consumption caused by having the telephones offsets any revenue the airlines get by having the telephones.

Thus, in that case, airlines may not benefit financially from having the telephones even though they collect a portion of the charge without having to pay for the equipment.

So, for the argument to work, this choice must be true.

Keep.

D. Even passengers who rarely or never use the in-flight phones prefer that airliners be equipped with them.

The argument doesn't rely on this assumption about the preferences of passengers who do not use the phones.

After all, regardless of what these passengers prefer, it could still be the case that, since airlines get revenue by having the phones but don't have to pay for them, airlines benefit financially by having the phones on their planes.

Eliminate.

E. The passengers who still use in-flight telephones are primarily those who are not carrying cell phones.­

This choice may be tempting if we're not clear regarding what we're looking for. After all, this choice is plausible. So, if we see that this choice is plausible and forget that we need a necessary assumption, we might choose it.

At the same time, this choice is incorrect. After all, we don't need a choice that's just plausible. We need a choice that states an assumption on which the argument depends, and the argument doesn't depend on any particular passengers using the phones. After all, as long as someone uses the phones, the airlines get a portion of the charges and thus may benefit financially.

So, regardless of whether this choice is true, the argument works.

Eliminate.

Correct answer: C