"Retired persons in the United States are unhappy about the level of assistance they receive from Social Security. After all, a report just published by the American Association of Retired Persons surveyed 30 retirees in all parts of the country and they all agreed that their Social Security benefits were insufficient" commits the fallacy of

I can see that there are no choices.

fallacy of bandwagon

Explanation:

A "logical fallacy" refers to the error of reasoning or logical gap that makes an argument invalid.

The situation above commits the fallacy of the bandwagon because the argument is being supported only according to a significant number of population. This is a fallacy because it doesn't necessarily mean all of the retired persons are unhappy about the level of Social Security assistance due to the opinion of 30 persons who agreed that they were unhappy. It becomes a "standalone justification" of the validity of an argument. We cannot judge the happiness or unhappiness of all retired persons according only to a group of 30 persons (even though they were chosen from different parts of the country).

So, this explains the answer.