再次免疫应答的主要抗体,也是唯一能通过胎盘的抗体是( )
A.IgGB.IgMC.IgAD.IgDE.IgE
参考答案:A
There is ________ pollution in the countryside than in the cities.
A. fewer B much C. less
在钢筋排布图集发行以前,主次梁交叉点处钢筋超高,是何原因?