The math’s problem remained confusing to the boy although ______ over and over.
| A．explaining | B．being explained | C．explained | D．having explained |
It is no good always complaining about life. ________ ，we are living.
| A．At least | B．Or else |
| C．What's more | D．Instead |
By the time he was twelve, Edison __________ to make a living by himself.
| A．would begin | B．has begun |
| C．had begun | D．was begun |
As its name indicates, the “American Host Family” program gets American families __________in foreign students' lives in America and offers homes for them.
| A．to involve | B．involving |
| C．involved | D．having involved |
A lot of tall buildings __________ in Shanghai in the past three years.
| A．have set up | B．have been set up |
| C．set up | D．were being set up |
John's success has nothing to do with good luck. It is his hard work __________ has made him what he is today.
| A．why | B．when |
| C．which | D．that |