Question

Scientists think that there has been life on Earth for _______ years.       

A. millions

B. millions of

C. million of

D. million

Answer 1

B

试题分析：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
点评：正确区分是确切数还是不确切数，二者不能混淆，关键是thousand和million加不加s。