量油孔内应装设（）制的导向槽，以免钢卷尺与孔壁和量油管摩擦而发生火花。

A、铁

B、钢

C、铝

D、铸铁

Passage One

If teachers want to find out if their students wrote their own papers, they ______.

A．ask other teachers to read their students’ papers

B．ask their students to list their sources of information

C．can sign up for the Internet service

D．search the Internet and compare papers