I spent half an hour ___ this difficult math problem.

A. to be interviewed

B. interviewing

C. being interviewed

D. interviewed

A. go out

B. went out

C. will go out

D. would go out

A. come B. would come

C. came D. have come

A. is

B. be

C must be

D. can be

A. If he took

B. If he should take

C. Were he to take

D. Had he taken

A. spoke

B. will speak

C. was going to speak

D. had spoken

A. will not like B. don’t like

C. had not liked D. might not like

A. give up

B. gave up

C. would give up

D. should give up

A. will have been finishing

B. would finish

C. will have finished

D. will be finishing

A. will finish B. has finished

C. finish D. would finish