维生素A缺乏症最早出现的表现是（） A.眼干燥，夜盲 B.皮肤干燥 C.毛囊角化性丘

血吸虫性肠病的虫卵主要沉积在：（）

A．肌层

B．黏膜和黏膜下层

C．浆膜

D．肠壁全层

单词题

1. Do you like lettuce in ______?(sandwich)

2. First put the oranges into the b______. After a while you can drink orange juice.

3. The students enjoy ______(have) birthday parties.

4. Let's ______(make) the milk shake together!

5. Put the ______(黄油) on a slice of bread.

6. If you a______ six to eight, you will get fourteen.

7. Here is a r______ for a great apple milk shake.

8. -What would you like, tea or milk?

    -Well, a c______ of tea, please.

植物生长是指细胞数目的增加，这是通过细胞分裂实现的．______．

由于超声波在传播时产生扩散和衰减，所以超声检测应尽可能在其近场区进行。

用来反映率的抽样误差的指标为（）

A．p

B．S

C．S_P

D．