双向锁定封隔器由芯轴和()分别带有左、右旋金属齿形螺纹的锁块组成。
A、一对
B、二对
C、三对
D、四对
参考答案:B
用适当的词填空。
1. My uncle likes ______ (run) very much. Look! He is running now.
2. Helen wants ______ (play) volleyball with Nancy.
3. Liu Tao ______ (not like ) Science at all.
4.The girl usually ______ (go) to bed at nine.
5. The old man is sitting ______ (quiet) under the tree.
6. The little girl ______ (like) making clothes.
7. Does your father sing ______ (good) ?
8. Su Yang and Su Hai ______ (be) the same age.
9. What ______ (do) your classmates usually do on Sundays?
10. The puppets ______ (jump) around on the bus.
越来越多的流通企业,承担起生产厂家的“采购代理”任务,是因为物流过程增加了产品的()
A、时间效用
B、空间效用
C、品种效用
D、批量效用