Here are two letters to George and his replies.

小题1:Alice is worrying about ________.

A. her friends   B. her marks             C. her height                   D her weight

小题2:Bob should ________ according to George’s letter.

A．take more exercise

B．talk to his friends

C．join a basketball team

D．learn some French.小题3:George advises Alice to talk to ________ for help.

A．her mother

B．her teacher

C．Bob’s teacher

D．Bob’s friends

滲碳式钢表面森如碳原子的过程。方法是将零件置于含碳的介质中加热和保温，使活性碳原子滲入钢的表面，以提高钢的表面含碳量，从而获得表面高硬度，中心（）的零件。