Life is not as smooth as we expected. We may have periods in our life ________ everything seems tough.
| A．when | B．where |
| C．which | D．that |
She went to the bookstore and bought _________.
| A．dozen books | B．dozens books | C．dozen of books | D．dozens of books |
It is no ________arguing with Bill because he will never change his mind.
| A．use | B．help | C．time | D．way |
At the meeting they discussed three different ________o the study of mathematics．
| A．approaches | B．means | C．methods | D．ways |
The ________on his face told me that he was angry．
| A．impression | B．sight | C．appearance | D．expression |
Always read the_______on the bottle carefully and take the right amount of medicine．
| A．explanations | B．instructions | C．descriptions | D．introductions |