When _____ his view about his job as a teacher, Mike said he found it very interesting and rewarding.

A．asking

B．asked

C．having asked

D．to be asked

目前我国最重要的交通运输方式是______，我国海拔最高的铁路是______．我国东西向的铁路干线有______我国南北向的铁路干线______．