I like ________ to Wangfujing to buy gifts.[ ]
A. go
B. goes
C. going
D. went
答案:C
2000千克=______吨7吨=______千克60秒=______分.
F-7型分配阀采用二压力机构与三压力机构相结合的混合机构。即能阶段缓解,又能()