已知每个木模的质量m木=5.6kg，木头的密度ρ木=0.7×103kg/m3．现

In the past my hometown was used to be a beautiful place. Thick trees and green grass could be seen in everywhere. In order to build house and grow more crops, people cut down more and more trees. With time went on, the whole forest was almost destroyed. Gradually the green hills have changed into wasteland. As a result, sandstorms struck us now and then, of which we suffer a lot. However, I do hope all the people should realize the terribly result of not caring about our environment. What's more, they should take good care of the forests and plant trees instead cutting them down to improve our living conditions. 

下图所示，这应该是下列哪个朝代大臣办公的地方 [ ]

A、唐朝

B、明朝

C、清朝

D、汉朝

案件的确认标准是什么。

确定砂浆强度等级时，应采用同类多孔砖（）为砂浆强度试块底模

A.正面

B.背面

C.正面和背面

D.侧面