1.— I called you at 4:00 yesterday afternoon, but no one answered. — Sorry, I _____ with my friends at that time.
A. swim
B. swam
C. will swim
D. was swimming
2.— Excuse me, where is Mr. Brown's office?— Sorry, I don't know. I _____ here for only a few days.
A. work
B. worked
C. have worked
D. will work
3.—Where is Bob?— He ______ to Harbin for a meeting.
A. went
B. has been
C. has gone
D. had gone
Don't make so much noise. The children _______ an English lesson.
A. have
B. are having
C. were having
D. had