流行性感冒病毒最容易发生变异的型别为()。
A.甲型流感病毒
B.乙型流感病毒
C.丙型流感病毒
D.乙型和丙型流感病毒
E.甲型和乙型流感病毒
参考答案:A
I ________ smoking in the end, because it is not allowed in public indoor places in our country now. [ ]
A. gave off
B. gave up
C. gave in
D. gave away
测量电压时,作法正确的是()。
A.表与电路并联
B.表与电路串联
C.红表笔接负极
D.黑表笔接正极