_______ of my parents are on holiday in Hainan now. [ ]
A. All
B. Any
C. Both
D. Some
答案:C
抽油机动态控制图合理区的特点是泵效与流压协调、()。
A、流压小于5MPa
B、泵况良好
C、系统效率高
D、参数合理