____is known to all, good friends _________ happiness and value to life.
| A．It; add |
| B．As; add |
| C．It; add up |
| D．As; add to |
—What does the sign over there read?―“No person ______ smoke or carry a lighted cigarette，cigar or pipe in this area．”
| A．will | B．may | C．shall | D．must |
— I heard they went skating in the mountains last winter.— It _____ true because there was little snow there.
| A．may not be | B．won’t be | C．couldn’t | D．mustn’t be |
I was really anxious about you. You _______ home without a word.
| A．mustn’t leave | B．shouldn’t have left | C．couldn’t have left | D．needn’t leave |
—We weren’t sure which way to go. In the end we turned right.—You _____ the wrong way. You _____ left.
| A．went; should have turned |
B．have gone; must turn |
C．went; would have turned |
| D．had gone; must have turned |
I lived with my sister this summer and didn’t have to pay rent. So I _____ save most of my salary.
| A．could | B．would | C．was able to | D．should |