采用水压驱动的油田，采收率（）。
A.较高
B.较低
C.不变
D.平稳
参考答案：A
Sit down, Emma. You will only make yourself more tired, ________ on your feet.[ ]
A. to keep
B. keeping
C. having kept
D. to have kept
税收具有的基本特征有（）
①强制性②固定性③无偿性④法制性
A.①②③
B.②③④
C.①②④
D.①③④
tired, ________ on your feet.[ ]