More than two years ago people knew little about the universe.A. thousandsB. thousandC. t

问题补充：

More than two years ago, people knew little about the universe.

A. thousands

B. thousand

C. thousands of

D. thousand of

答案：

A. thousands

(答案→)B. thousand

C. thousands of

D. thousand of

解析：此题考查名词的量。确切数量常用数词+hundred/thousand/million/billion+名词的复数形式；不确切数量常用hundreds/thousands/millions/billions + of+名词的复数形式.