目前认为再障的发病机制主要有()
A.免疫机制异常
B.遗传倾向
C.造血干细胞异常
D.造血微环境缺陷
E.物理因素
参考答案:A, B, C, D
—Will you buy the red T-shirt or the black one?
—I will buy ______ of them. One is for my brother and the other is for my father.
A.both
B.either
C.neither
D.all
在四冲程柴油机动力装置中,废气锅炉的排气进口温度t1约为400℃大约可利用排气余热的(),而二冲程柴油机动力装置的t1为200—3O0℃,则可利用排气余热的()左右。
A.62%/30%
B.62%/40%
C.40%/62%
D.30%/62%