一个具有单属性键和n（n＞0）元组的关系，如果对这个关系的键属性做一个投影，那么投影

阅读短文，选择正确答案。

      This is a picture of Mr. Brown's family. In the picture we can see Mr. Brown is sitting on a sofa. He is

reading the newspaper. Mrs. Brown is sitting near the computer. She is sending an e-mail to her mother. Mike

is 10 years old. He is a pupil. He is watching TV. Alice is 5 years old. She is playing with toys on the floor.

1. This is a picture of _____________.

A. Mr. Green's family

B. Mr. Brown's family

2. Where is Mr. Brown?

A. He is in the park.

B. He is sitting on a sofa.

3. What is Mr. Brown doing? 

A. He is playing chess.

B. He is reading the newspaper.

4. Is Mrs. Brown sitting near the computer?

A. Yes, she is.

B. No, she isn't.

5. How old is Mike?

A. He is 9 years old.

B. He is 10 years old.

函数f（x）=x³+4x+5在x=1处的切线与y轴的交点为______．

没有牙合关系的牙合位是（）

A.正中牙合位

B.下颌息止牙合位

C.正中关系

D.肌位

E.下颌后退接触位

下列生物制品，按照药物妊娠毒性分级，属于B类的药物是（）

A.奥曲肽

B.干扰素

C.利妥昔单抗

D.胰脂肪酶

E.免疫球蛋白

中国联通围绕公司全业务统一品牌战略，面向3G和全业务，建立了统一、规范、系统的“（）+（）+（）”的服务体系。