88. ---Must I finish my homework now?-- No, you ____.
You may have a rest first.
A. mustn’t B.
can’t C. may not D. needn’t
89-Why is the man running in the street? --He _____ for exercise.
A. might run B. might be C. might be running
90 We were late for class ____ the heavy rain.
A. because B. because of C. so
91I didn't come to school yesterday____ I had to look after my grandmother
at home.
A. because B. because of C. since