Can you imagine what problem may ______ when human beings are cloned?
| A．raise | B．cause |
| C．arise | D．lead |
---Alice, why didn’t you come yesterday?
--- I______, but I had an unexpected visitor.
| A．had | B．would | C．was going to | D．did |
His parents are very concerned about his son at school because he _______moving in his seat.
| A．is always keeping | B．always keeps | C．does keep | D．has always kept |
--- _____ the population of China? --- About 1.3 billion.
| A．What is | B．How many are | C．How much is | D．What are |
We look forward to the day when motorcars will be replaced by some less dangerous ____ of transport.
| A．means | B．methods | C．manners | D．ways |
Mother _________father to give up smoking, but she failed.
| A．persuaded | B．tried to persuade | C．suggested | D．to tell |