Despite his great efforts,he ______unsuccessfully after all.

A．ended in

B．ended with

C．ended up

D．turned out

为了开采石油和天然气，在油田勘探开发过程中，凡是为了从地下获得石油而钻的井，统称为（）。

A.水井

B.探井

C.油井

D.生产井