Many species have become extinct each year before biologists can identify them.

A. If it hadn't been for this treatment, the patient would have died.

B. Unless the patient hadn't had this treatment, he would have died.

C. Had not the patient had this treatment, he would have died.

D. But for the patient had had this treatment, he would have died.

A. most

B. mostly

C. chiefly

D. best

A. The owner of the house is thought to go abroad.

B. The owner of the house is thought to have been going abroad.

C. The owner of the house is thought to have been gone abroad.

D. The owner of the house is thought to have gone abroad.

A. I didn't have a chance to meet my old English teacher because I left school.

B. This is the last time I met my old English teacher at school

C. I last met my old English teacher when I left school.

D. My old English teacher hasn't met me since I have left school.

A. attacks

B. repeats

C. roofs

D. trays

A. as soon as her boss returned

B. until her boss will return

C. by the time her boss returns

D. when her boss will return

A. has been worked

B. has worked

C. had been working

D. was working