Which of the following most probably means what you hear

A．Everybody has opportunities if he is ready for them.

B．Some people have opportunities and are ready for them.

C．All people have opportunities, but only some people seize them.

D．Opportunities come to people when they are not ready.

生产矿井必须建立水文观测系统，并按规定时间坚持观测。受水害威胁的工作面也应定期观测。