My father with my mother __________ my grandparents’ home every Sunday.

A．is going

B．are going

C．is going to

D．are going to

普通型调速阀稳定流量主要是靠自动改变（）开度。

A.节流阀

B.定差减压阀

C.定差溢流阀

D.定值溢流阀