用手工电弧焊一钢结构，选用E5015、φ4.8焊条，求应选用多大的焊接电流？[已知I

During our two months on the road, Bennett and I had a really (1) experience with a good, honest (2) and some helpful mechanics.

We were driving east on Highway 10 when our "chick engine" light came on. We limped of a(n) (3) into Las Cruces. We had a real car (4) Bennett nursed the ear into a local garage. By this time the car was missing so (5) it was shaking all over. This was the (6) time to arrive at a garage—late Friday afternoon. Service adviser Scott was busy (7) paper work and customers as we (8) our problems. (9) he was already "ten cars behind", he told us to pull the car into the garage.

Lincoln, who we later (10) was one of the two motor technicians, took (11) of our car repairing. He and Scott and some other mechanics stayed several hours after closing, (12) the car.

Early the next morning (the shop was officially closed on Saturdays), Lincoln finally located the (13) and fixed it easily within only (14)

Later Scott (15) out to us that it was our attitude that helped. "You didn’t come into the place demanding this or that. You showed an (16) of our problems on a busy Friday afternoon. Customer’s attitude means a lot. " He was right in some way, customers should show (17) and understanding to people who (18) them. (19) people were extremely busy, they found way to at least try and help when they are met with politeness.

The pleasant experience I had shows that (20) for other people can always help.

3().

A.exit 

B.turning 

C.crossing 

D.entrance

2L容积不变的密闭容器中，加入1．0molA和2．2molB，进行如下反应：

A（g）+2B（g）C（g）+D（g），在不同温度下，D的物质的量n（D）和时间t的关系如图

试回答下列问题

（1）800℃时。0-5min内，以B表示的平均反应速率为_________________。

（2）能判断该反应达到化学平衡状态的标志是_________________。

A．容器压强不变

B．混合气体中c（A）不变

C．2v正（B）=v逆（D）

D．c（A）=c（C）

E．混合气体的平均分子量不再改变

F．混合气体密度不变

G．A:B:C:D= 1:2:1:1

（3）利用图中数据计算800℃时的平衡常数K=________，B的平衡转化率为：________。该反应为

________反应（填吸热或放热）。

（4）700℃时，另一2L容积不变的密闭容器中，测得某时刻各物质的量如下：n（A）=2．2mol，

n（B）=5．2mol，n（C）=1．8mol，n（D）=1．8mol，则此时该反应________进行（填“向正反应方向”“向逆反应方向”或“处于平衡状态”）。

两球相向运动，发生正碰，碰撞后两球均静止，于是可以判定，在碰撞以前（   ）

A．两球的质量相等

B．两球的速度大小相等

C．两球的动量大小相等

D．以上都不正确

现况研究主要分析指标是（）。

A.死亡构成比

B.某病的患病率

C.某病的发病率

D.某病的二代发病率

E.某病的死亡率

眩晕的常见病因有（）

A.情志不遂

B.饮食不调

C.外感六淫

D.跌仆外伤

E.体虚年高