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.