下列属于测量流量的仪器有（）
A.流量计
B.测压计
C.压差计
D.比托管
参考答案：A
We first met on a train in 2010，but we both felt immediately that we ________ each other for years.
A．knew
B．have known
C．had known
D．know
胎儿发育到约______周成熟，成熟的胎儿从母体的______产出，这个过程叫做分娩．
