平衡压力钻井
参考答案：
指钻井中，使井底压力等于地层压力的情况下钻井，称为平衡压力钻井。
The magician picked several persons ______ from the audience and asked them to help him with the performance.
A．by accident
B．at random
C．on occasion
D．on average
根据经济法主体行为的层级性，在税法领域，税收的征收行为是基础性的行为，而税收调控行为则是高层次的行为。( )
