下列属防止轨道爬行的措施有()。
A.铺设防爬设备
B.松动中间扣件的扣压力
C.经常压紧浮起道钉
D.调整轨缝,松动夹板和螺栓
参考答案:A, C
— If we go on polluting the world, it won’t be fit for us to live in.
— ____. We’ve got to do something about pollution.
A.That’s all right.
B.I couldn’t agree more.
C.No way!
D.What a shame!
简述HLA抗原的分布。