We must study hard, because we shouldn’t _______ our parents _______ .

A. make; down   B. let; up        C. help; happy    D. let; down

We must study hard, because we shouldn’t _______ our parents _______ .

1. A.
   make; down
2. B.
   let; up
3. C.
   help; happy
4. D.
   let; down

We must study hard, _______ we'll fail in the exam.

1. A.
   but
2. B.
   and
3. C.
   so
4. D.
   or