I don't know _____ I should buy a present. [ ]
A. what
B. if
C. which
D. as
答案:B
自动调节器的基本运算规律包括()。
A.P
B.I
C.PID
D.ID
肺血栓栓塞症常见的胸部X线改变有()
A.球形病灶
B.肺叶局部片状阴影
C.肺动脉高压征及右心扩大征
D.肺门改变
E.肺动脉阻塞征