正常人钙、磷（mg/dl）乘积为（）
A.16～20
B.26～30
C.36～40
D.46～50
E.56～60
参考答案：C
I’ve included some photos in my letter will help you picture the places I
worked as a volunteer teacher.
A．that, which
B．which, where
C．which, that
D．\, in which
中、低压法兰平面与管道中心垂直的倾斜公差，φ300毫米以上的管子为（）
A.2毫米
B.3毫米
C.4毫米
