Tom as well as his friends ____ to visit our school soon after they arrive in Changsha.

A．is coming

B．are coming

C．will have come

D．has come

压力表（）的选择，应以合理、实用、经济为原则，在满足工艺生产要求前提下，昼选用精度较低的压力表。

A.精度等级

B.量程大小

C.类型

D.型号