旋转阳极X线管定子的极数一般是
A．5
B．4
C．3
D．2
E．1
参考答案：D
解析：旋转阳极X线管定子的极数一般为两极。
The telephone ______ three times in the last hour, and each time it _____ for my father.
A．had rung; was
B．has been ringing; is
C．rang; has been
D．has rung; was
李杲治疗内伤热中证的用药法度是什么？
