________ at the door before you enter my room, please．

A．Knock

B．Knocking

C．Knocked

D．To knock

Our friendship ________ quickly over the weeks that followed．

A．had developed

B．was developing

C．would develop

D．developed

Many people have donated that type of blood; however, the blood bank needs ________．

A．some

B．less

C．much

D．more

________ with care, one tin will last for six weeks．

A．Use

B．Using

C．Used

D．To use

When deeply absorbed in work, ________ he often was, he would forget all about eating or sleeping．

A．that

B．which

C．where

D．when

George said that he would come to school to see me the next day, but he ________．

A．wouldn't

B．didn't

C．hasn't

D．hadn't

Jerry did not regret giving the comment but felt ________ he could have expressed it differently．

A．why

B．how

C．that

D．whether

One learns a language by making mistakes and ________ them．

A．corrects

B．correct

C．to correct

D．correcting

By the time you have finished this book, your meal ________ cold．

A．gets

B．has got

C．will get

D．is getting

It's so nice to hear from her again ________, we last met more than thirty years ago．

A．What's more

B．That's to say

C．In other words

D．Believe it or not