The united states is one of only four countries in the world with a minimum legal drinking age of 21. clearly, then, we should change our drinking age.
a) true
b) false

It is TRUE that the United States is one of only four countries in the world with a minimum legal drinking age of 21.

Explanation:

The other three countries with a minimun legal drinking at the age of 21 are Indonesia, Mongolia and Palau. The comment on this can be that limiting the  the drinking age to 21, won't necessary bring better results on drinking behavior.

This means that weather the age is reduce or kept at 21, the main thing is to educate young adults  on how to drink and be safe. For instance not to drive, or to learn that drinking is not bad, but drinking in excess its what can be harmfull.

the answer is:

c. economic output