已证实与人类白血病的发病有密切联系的病毒是（）. A.EBV B.CMV C.HBV

将多项式15x³y²-5x²y+20x²y³因式分解时应提取的公因式为（　　）

A．5xy

B．5x²y

C．5xy²

D．5x²y³

用所给词的适当形式填空。

1. I think you have made a good               (decide).

2. He told me that he               (go) to the beach the next day.

3. We're supposed               (finish) homework on time.

4. The boys               (play) soccer when I got there.

5. My parents               (buy) me a new bicycle yesterday.

6. The children enjoyed               (they) on the Great Wall.

7. I like swimming because it can make me               (keep) fit.

8. The yellow pants are               (cheap) of all.

使用厘米刻度尺测一根电线的长度，测量结果记录正确的是[ ]

A.23.260m　　　

B.23.2600m　　　

C.23.26m　　　

D.23.3m　

商业模式的设计步骤，第一步是（）

A、创意构思

B、需求分析

C、客户测试

D、原型设计

E、评估反馈

下列属于妊娠禁用药的是( )

A．制川乌

B．白附子

C．马钱子

D．丁公藤

E．肉桂