短文改错

Dear Mary,

     We've been pen friends for a year now.It's a fun,isn't it?This year I'm starting my college life.I'm real

excited.Everything will be different with things in high school.I'll have more classes,and each of the class

will be in a different classroom.In the dormitory I will have a locker which I can keep my textbooks,

notebooks,coats and other thing.This is my favorite thing about going college.Two students will have to

share a locker.I will like my friend Kim to be my locker partner.We're thinking of put our favorite pictures

on the locker door.Please sending me a            

        new picture of yourself!OK?

        Well,write soon.Bye.

改错____________________________________________________________________________

液控单向阀在系统中主要用途有（）。

A.对液压缸进行锁闭

B.作立式液压缸的支承阀

C.作背压阀

D.作顺序阀

E.某些情况下起保压作用