轮状病毒感染后产生的最重要的特异性抗体是
A．IgA
B．IgB
C．SigA
D．IgM
E．IgG
参考答案：C
We often practice _______. [ ]
A. to play football
B. playing football
C. playing the football
D. to play the football
意见领袖有哪些作用？
