— It shouldn't take long to clear up after the party if we all volunteer to help. 

— That's right. ______. [ ]

A. Many hands make light work

B. Something is better than nothing

C. The more, the merrier

D. The sooner begun, the sooner done

表明地层形成先后顺序的时间概念称为（）。

A、地质单位

B、地质现象

C、地质年龄

D、地质时代