胸部摄片高千伏摄影是指()
A．≥90kV
B．≥100kV
C．≥110kV
D．≥120kV
E．≥130kV
参考答案：D
— How long do you suppose it is _____ he arrived here?
— No more than half a week.[ ]
A. since
B. before
C. after
D. when
心房梗死可导致PR段改变。（）
