问题补充:
Scientists think that there has been life on Earth for years.
A. millions
B. millions of
C. million of
D. million
答案:
解析:此题重点考查数词的表达法,如果有确切的数字 thousand 或million后面直接跟名词,thousand 和million等不用复数,也不用of,而thousands of,millions of直接跟名词或代词,前面不用确切的数字表示约数,根据题意故选B