工作岗位评价的要素分为（）几类。

A.主要因素、一般因素、次要因素、极次要因素

B.高度相关或显著相关

C.低度相关或无相关

D.质量、产量、安全、消耗、技术

By careful observation and precise calculation, Nicolaus Copernicus _____ that there is no one center

in the universe and the sun is the center of the solar system.    [ ]

A. believed    

B. thought  

C. concluded  

D. imagined