公元前60年西汉王朝在西域设置西域都护，这是今新疆地区正式归属中央统辖的开始，距

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     It is a Saturday morning, Mr Black and his child, Bill are in a big shop. The shop sells clothes and

school things. Mr Black wants to buy a new sweater for his wife. Bill would like a T-shirt. So his father

buys a green one for him. Bill wants to buy some picture books and color pencils, too. There are many

things and many people in the shop. They are men and women, old and young. They all like to buy

something there. The workers in the shop are friendly.

1. Mr Black goes to the shop with___________

A. his son

B. Mrs Black

C. his father  

D. other old people

2. Mr Black is going to buy a new sweater for __________

A. Mrs Black  

B. Bill

C. his friend  

D. his son

3. Mr Black buys ______for Bill.

A. a T-shirt

B. a sweater

C. shorts  

D. a hat

4. People in the shop are ________

A. old and young  

B. men and women

C. A and B  

D. young

5. Does Mr Black buy Bill picture books?

A. No

B. Yes

C. It's green

D. We don't know

当温度降低时，晶闸管的触发电流会增加、正反向漏电流会下降；当温度升高时，晶闸管的触发电流会下降、正反向漏电流会（）。

简述生态因子作用的不可替代性和补偿性，并举例说明。

动机

小麦外部形态在拔节初期时，其内部穗分化处在（）。

A.小穗原基分化期

B.单棱期

C.四分体分化期

D.小花原基分化期