----I am going to Qingdao and stay there for a week.

----______ you are there, would you please buy some books for me?

A．If

B．While

C．Since

D．As soon as

由于建筑施工要求，某试验室受工程单位委托对某粒径小于5mm的黏性土样进行击实试验，从而确定土的最大干密度与相应的最优含水量。
请根据上述条件，回答下列问题。

进行击实试验时，轻型击实筒分为几个层击实每层有多少击