对于无糖尿病高危因素的孕妇，糖筛查的最佳时间是A．20～24周B．23～25周C．2

以下细胞在接触性超敏反应的诱导期起主要作用的是（）。

A.颗粒层细胞

B.朗格汉斯细胞

C.肥大细胞

D.淋巴细胞

句型转换。

1. He is poor, but he always has a good time. (改为同义句)

                    he is poor, he always has a good time.

2. The boy on the black bike is my little brother. (对画线部分提问)

                    ________is your little brother?

3. How do you like the song Yesterday Once More? (改为同义句)

                    do you                 of the song Yesterday Once More?

4. Whatever you do, don't sleep all day. (改为同义句)

    _______                                  you do, don't sleep all day.

5. Roy enjoyed himself at the party last Sunday. (改为同义句)

    Roy                                              ________ at the party last Sunday.

下列词语中斜体的字注音（用汉语拼音方案）。（2分）

（和）平

致密星体

在n次重复试验中，事件A出现了m次，则m/n称为事件A的( )。

A．频数

B．频率

C．概率

D．频度