more thsn two ___years ago,people knew little about the universe

题目

more thsn two ___years ago,people knew little about the universe
A thousands B thousand
C thousand of D thousands of
哪一个是正确答案 为什么?

答案

应该选b
thousand 是个数量词 不用加s
thousands of years 是上千年的,没有确指.