关于麻疹的流行病学特点，正确的是 A．病人是惟一的传染源，前

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问题多项选择题

关于麻疹的流行病学特点，正确的是

A．病人是惟一的传染源，前驱期和出疹期均有传染性

B．以呼吸道飞沫传播为主

C．病后获持久免疫力

D．恢复期病人存在携带病毒的现象

E．主动免疫是预防麻疹的重要措施

答案

参考答案：A,B,C,E

听力题

小题1:They had left the (行李)at the station.

小题2:She had to tidy the classroom as (惩罚)for being late.

小题3:The first step in the (步骤)for making a kite is to build the frame.

小题4:Old people are usually more (保守的)than young people .

小题5:He drove his car with (谨慎).

小题6:A (稳定的)government is essential to economic growth.

小题7:He whipped out a (手帕)to bind up his finger.

小题8:She replied without (犹豫).

小题9: (删除)his name from the list.

小题10:The morning’s work was constantly, (打断)by phone call.

选择题

遗传学上将某种分子上决定一个氨基酸的三个相邻碱基称为“密码子”，这种分子是[ ]

A．肽键

B．DNA

C．mRNA

D．tRNA