人群对某种传染病易感性增高的原因是()
A.该传染病流行过后
B.人群中一般抵抗力的提高
C.人群中自动免疫的推广
D.病原体的变异
E.抗生素的广泛应用
参考答案:D
—How much do you know about the Youth Olympic Games to be held in Nanjing?
—Well, the media ________ it in a variety of forms.
A.cover
B.will cover
C.have covered
D.covered
小气道的概念是()。
A.内径<2μm
B.内径<1mm
C.外径<2mm
D.内径<2mm
E.外径<2μm