Riding a bicycle can be fun. But ______ you ride a bike to work, and then there isn’t one to ride home?
| A．how come | B．what if |
| C．no matter how | D．wherever |
Scientist are not sure about the ___________ of water on the Mars.
| A．occupation | B．existence | C．demand | D．treasure |
Don’t push me! __________ you know the truth right away?
| A．Must | B．Could | C．Might | D．Would |
. He __________ full marks, but he was so careless as to make a spelling mistake.
| A．must have gained | B．can have gained | C．could have gained | D．must gain |
Then I have learned there are a lot of troubles in our lives, but the problem is __________ they control you or you control them.
| A．why | B．whether | C．that | D．what |
--- Mr White is strongly against the plan.
--- __________ ? It was he who suggested it.
| A．Why not | B．How’s that | C．What for | D．Is that right |