患者因乏力、心悸、头晕、感染、发热2个月来医院检查,诊断为再障,其发病首位病因是()
A.药物及化学物质
B.电离辐射
C.感染
D.慢性失血
E.遗传
参考答案:A
生物界最基本的分类单位是_____,又叫________。
It seems water______from this tap for some time. We'll have to take it apart to put it right.
A. had leaked B. is leaking C. leaked D. has been leaking