用所给动词的适当形式填空。

     In many countries, 1_________ (smoke) is becoming a bigger problem for young people. Most

smokers 2_________ (start) in their teens (years of a person's age from 13 to 19) or even earlier.

     A study of 8,000 Beijing students last May 3_________ (show) us that smoking was a problem

for many Chinese kids. More than 21% of middle school students and 6% of primary school pupils

(小学生) said they had smoked.

     "If young people start 4_________ (smoke) early, they will probably get addicted to nicotine

(对尼古丁瘾). And it 5__________ (be) very hard to give up (放弃) later on," said a professor.

     Every year, about 4 million (百万) people die (死亡) of smoking. And if people keep 6_________

(smoke), that number will go up to about 10 million a year by 2030, the World Health Organization

(WHO, 世界卫生组织) says. So we have to 7_________ (know) and tell others about the dangers

(危险) of smoking. Everyone of us should 8_________ (do) something useful to stop kids from 

9_________ (smoke), or one day we 10_________ (see) what we won't see.

1._______ 2._______ 3._______ 4._______ 5._______

6._______ 7._______ 8._______ 9._______ 10._______