焊接工艺评定中（）是指影响焊接接头冲击韧性的焊接工艺因素。

体内唯一能产生抗体（免疫球蛋白分子）的细胞是（）。

A.T细胞

B.B细胞

C.NK细胞

D.LAK细胞

E.eLAK细胞

在对话的空白处填上适当的句子，使对话意义完整，语法正确。

A: Hi, Xiao Peng, long time no see. 1_______?

B: I have been to my hometown.

A: 2_______?

B:Yes. But I felt a little sad.

A: 3_______?

B: I saw many kinds of pollution in my hometown.

A: 4_______?

B: Yes, first, the water pollution. In the past,the water in the river was clean and there

     were a lot of fish in it.But now the water is very dirty.

A: Oh, it's a great pity.

B: Second, I can see white pollution everywhere.

A: I think we should do something for your hometown.

B: Thanks. The local government has done something to protect the environment.

A: Good, 5_______?

B: Yes, I will. I want to see what I can do for it.

A: OK. Let's join hand.

某猪场猪突然发病，传播迅速，病猪跛行明显，表现蹄壳变形或脱落，卧地不能站立。部分猪在鼻镜、吻突、 * * 等处皮肤出现大小不一的水疱，水疱很快破溃，露出边缘整齐的暗红色糜烂面，形成烂斑，病死率较低。剖检死亡猪，见心包膜有弥散性出血点，心肌切面有灰白色或淡黄色斑点或条纹。发生该病，猪场应立即（）

A.上报疫情

B.隔离

C.封锁

D.扑杀

E.消毒

已知R1=R2=R3=3，这三个电阻并联后的总电阻也是3。

曲线

的渐近线条数为( )