Mr. Green is said _____ an experiment to prove the new method of solving the problem when young.
| A．to do | B．to have done | C．to be doing | D．to have been doing |
Bob would have helped us yesterday, but he_______
| A．was busy | B．is busy | C．had been busy. | D．will be busy |
Green products are becoming more and more popular because they are environmentally_______.
| A．friendly | B．various | C．common | D．changeable |
Heavy rainstorm broke out in South China,68 lives and 62 still missing.
| A．killing ,leaving | B．killing ,left | C．killed, leaving | D．to kill , leave |
Dr. Smith, together with his wife and daughters , visit Beijing this summer.
A is going to B are going to C was going to D were going to
The experiment shows that proper amounts of exercise, if regularly, can improve our health.
| A．being carried out | B．carrying out | C．carried out | D．to carry out |