英语填空millions of words have been w_____ about young people in

Millions of words have been written about young people in the USA.
答案：written
解析：
1.本句意思是：已经数百万个字写到了美国的年轻人.或者“在美国已经有数百万字写到了年轻人”
2.这里是被动语态,主动为：Someone has written Millions of words about young people in the USA.
There are reasons for this great interest in their ideas,feeling and actions.
答案：interest
解析：
1.本句意思是：就这种对他们的观念、感情和行为倍感兴趣而言是有原因的.
2.Interest in … 在某个方面的兴趣
Today there are about seven million American in colleges and universities.
当前高等专科学校和综合大学有七百万美国人.
Young persons under twenty-five make up nearly half of American population.
答案：under / population
解析：
1.本句意思是：25岁以下的青年人构成了近一半的美国人口.
2.under twenty-five 用作young persons 的后置定语；
3.make up 意思是“构成、组成”,无疑指的是构成人口.