人体感染病毒后最先出现的抗体是()
A．IgG
B．IgA
C．IgD
D．IgM
E．IgE
参考答案：D
I prefer taking exercise in my spare time ＿＿ healthy.
A．to keep
B．to keeping
C．rather than keeping
D．rather than keep
接种疫苗一定会成功。（）
