当我们要绘制一个正圆时应按住什么键（）A.ＳＨＩＦＴ。 B.ＡＬＴ。 C.ＥＳＣ。

从A、B、C、D中， 选出能替换下面句子画线部分的内容的选项。

1. —How are you, Jack?

    —I am OK.

A. Good

B. Nice

C. Fine

D. great

2. This is Mr. Huang. He is an English teacher.

A. He's

B. It's

C. His

D. It is

3. My grandmother and grandfather like vegetables very much.

A. parents

B. grandparent

C. grandparents

D. parent

4. My father eats eggs for breakfast. He likes them very much.

A. has

B. is

C. likes

D. meets

5. I have no balls, but Jim has.

A. doesn't have

B. am not

C. am not have

D. don't have

.质量是指商品的

A．使用价值

B．交换价值

C．价值

D．价格

医德监督

请至少说明GIF格式的两种特点：（）；（）。

电子皮带秤的称量长度如何确定？