在海上油田，自动控制系统的控制方案主要有（）。
A、三种
B、四种
C、五种
参考答案：A
Two thirds of the subway construction________so far and people will enjoy a fast and convenient trip
under the city early next year. [ ]
A. have been completed
B. is being completed
C. has been completed
D. will be completed
人工呼吸的次数一般为是
A．12～16次∕分
B．18～24次∕分
C．20～30次∕分
D．15～20次∕分
