Recently the Ministry of Environmental Protection issued a circular saying that China may adopt flexible working hours and stop school classes_____the highest air pollution warnings.

A．for fear of

B．in terms of

C．on top of

D．in case of

溶血空斑形成试验中，空斑的大小表示（）

A.抗体生成细胞的多少

B.抗体生成细胞的种类

C.细胞的大小

D.抗体生成细胞产生抗体的多少

E.吞噬细胞的活性