Environmental experts point out that ______ some serious problems such as global warming, but it also could threaten human life.
| A．not only does increasing pollution cause |
| B．not only causes increasing pollution |
| C．not only increasing pollution causes |
| D．not only increasing pollution does cause |
________ I be free tomorrow, I would go with you.
| A．Could | B．Should | C．Might | D．Must |
If he ________ my advice, he wouldn't have lost his job.
| A．followed | B．should follow |
| C．had followed | D．would follow |
This printer is of good quality.If it ________ break down within the first year，we would repair it at our expense.
| A．would | B．should | C．could | D．might |
Maybe if I ________ science，and not literature then，I would be able to give you more help.(2011·北京)
| A．studied | B．would study |
| C．had studied | D．was studying |
Sorry，I am too busy now.If I ________ time，I would certainly go for an outing with you.(2012·湖南)
| A．have had | B．had had | C．have | D．had |