气体保护焊焊接后不能用水降温的原因是什么()
A、会使焊缝变脆
B、会使焊缝生锈
C、会使焊缝变软
参考答案:A
Rearrange the words.连词组句。
1. is, snowy, It (.)
___________________________________________
2. have, I, dinner, my, family, with (.)
3. go, I, to, o'clock, school, at, seven (.)
4. time, is, it, What (?)
正常人精液在排精30~60分钟内,精子活动率应()
A.>20%
B.>40%
C.>50%
D.>70%
E.>90%