________________ he will come back this week or next week is not decided .
| A．That | B．Whether | C．When | D．If |
He is only too ready to help others, seldom, _____, refusing them when they turn to him.
| A．if not | B． if ever | C．if any | D．if so |
It is in their ability to speak ______ humans ______ from animals.
| A．which; differ | B．that; different | C．which; different | D．that; differ |
Tom, look at your shirt! It requires ________.
| A．washing | B．washed | C．to wash | D．being washed |
I am concerned ____ it that I can’t concentrate ____ my work because of headache.
| A．of; on | B．of; of | C．about; on | D．about; to |
_____of danger in the street at night, she had to go home, with a friend_____ her.
| A．Warned; accompanied | B．Warning; accompanying |
| C．Having warned; accompanied | D．Having been warned; accompanying |