I wish to thank Mr. Lord, without _______ help I would never have got this chance.

I saw Mr Li at the meeting yesterday.— Did you? He ______ have attended, for he had asked for sick leave.

Mike is a good boy. He often _________ to help his classmates.

The computer doesn’t work again. It __________. [ ]

20. _________raining hard for 3 hourswithout stopping.21.