镰刀型细胞贫血症是一种遗传病，隐性纯合子(aa)的患者不到成年就会死亡，可见这种

比一个数的3倍少3的数是10，求这个数的算式正确的是（　　）

A．（10-3）÷3

B．（10+3）÷3

C．（3-3）×10

D．3×10-3

可持续发展问题世界首脑会议又简称“地球峰会”，每( )年举行一次。

A．10

B．20

C．5

D．8

用所给词的适当形式填空。

1. The film is very _____ (surprise) and I'm( surprise) at it．

2. She _____ (buy) some flowers for her mother yesterday.

3. While I was _____ (shop), I saw my best friend.

4. The train usually _____ (leave) the station at ten o'clock in the morning.

5. I _____ (shop) in a supermarket when you called me up.

6. It's _____ (usual) for the trees to flower so early.

7. How about _____ (go) for a drive?

8. Listen! Someone _____ (knock) at the door.

9. What _____ you _____ (do) at 9:00 am. yesterday?

10. I _____ (wait) for the bus this time yesterday.

布氏杆菌病为人畜共患性传染病，其主要传染源为（）

A.患者

B.带菌者

C.病马

D.病猪

E.病羊

下列属于矿物质饲料的是（）。

A、玉米

B、磷酸钙

C、维生素A

D、鱼粉