Which sentence is not a proposition?
a. you can ride in a wagon.
b. you are late.
c. sit down.
d. terrie eats.

The sentence that is not a proposition (or a simple statement) is C. Sit down, because it is an order, not a statement. 

In 2081, everyone is equal not only in the eyes of the law but in every way; nobody is smarter, more athletic, better looking, etc. than anyone else. hazel is of average intelligence, which means she can't think about anything except in short bursts, and george has an intelligence way above normal.