X线束的最短波长取决于()
A.毫安
B.时间
C.千伏
D.毫安秒
E.靶物质
参考答案:C
What does his mother look like? [ ]
A. She's a doctor
B. She is forty
C. She is thin
D. She works in a bank.
通过垂直传播引起胎儿畸形的最常见病毒是风疹病毒和()。