No one knows exactly when our ancestors started talking，but new evidence suggests _______might have happened a long time ago．
| A．which | B．what | C．it | D．they |
There is no doubt ______ smoking can seriously damage our health.
| A．that | B．whether | C．why | D．which |
A small plane crashed into a hillside five miles east of the city, ____all four people on board.
| A．get along | B．kills | C．killing | D．to kill |
______ and short of breath, Andy and Ruby were the first to reach the top of Mount Tai..
| A．To be tired | B．Tired | C．Tiring | D．Being tired |
She was leaning against a tree as if ______ for someone.
| A．waited | B．wait | C．to wait | D．waiting |
The weather turned out to be fine yesterday. I ___ the trouble to carry my umbrella with me.
| A．should have taken | B．could have taken | C．needn’t have taken | D．mustn’t have taken |