应当按照气锁方式设计更衣室，使更衣的不同阶段分开，尽可能避免工作服被微生物和微粒污染。更衣室应当有足够的换气次数。更衣室后段的（）应当与其相应洁净区的级别相同。必要时，可将进入和离开洁净区的更衣间分开设置。一般情况下，洗手设施只能安装在更衣的（）。

The Great Wall was made not only by _____, but also the flesh and blood of _____ men. [ ]

A. earth and stone, millions of

B. earths and stones, millions

C. the earth and stone, million of

D. the earths and stones, millions