隔膜泵是通过调节()来改变隔膜薄膜片的弯曲程度,从而调节泵的排出量的。
A、电机转速
B、活塞冲程
C、入口液位
D、入口压力
参考答案:B
排球技术主要由()和()两部分组成。
The library along with bookstores ________ reading materials. It's open from 9?00 a. m. to 4:00
p. m. on weekdays. [ ]
A. provides
B. is providing
C. has provided
D. provided