What sentences are grammatically correct us students have a lot of work to do please return the book to us when you've read it who did you sell your old car to?

Answer 1

I think the only one that is grammatically incorrect is "Us students have a lot of work to do" it should be "WE students have a lot of work to do" .....

Answer 2

All three sentences are grammatically correct. Each one follows the standard subject-verb-object structure and uses appropriate punctuation.