下列传染病中,病后可获持久免疫力的有()
A.麻疹
B.水痘
C.流行性腮腺炎
D.脊髓灰质炎
E.乙脑
参考答案:A, B, C, D, E
—_________I borrow your lighter for a minute?
—Sure, no problem. Actually, you _________keep it if you want to. I’ve given up smoking.
A.Can; can
B.Should; may
C.Must; can
D.May; must
机械加工工艺过程中,用粗基准安装是必不可少的。