Most students think this book is useful as it _______ all the basic grammar rules they need to know.

A．deals

B．covers

C．says

D．teaches

架桥机焊接构件用焊条、焊丝和焊剂应与（）的材料相适应。

A.大臂

B.被焊件

C.前支腿

D.行走轮