配电线路开关采用负荷开关时，对联络线转供下游非故障区进行过载预判，满足转供条件再自动合闸联络开关，恢复非故障区域供电（）

此题为判断题(对，错)。

此题为判断题(对，错)。

A．危急

B．严重

C．一般

D．关注

试证连续函数f(x)是周期函数的充要条件是：存在T＞0，使对一切的x有∫_x^x+Tf(t)dt=∫₀^Tf(t)dt

sent. On Christmas Eve when Paul came out of his office, a street urchin was walking around the shiny new car, admiring it. “Is this your car, Mister?” he asked.

Paul nodded. “My brother gave it to me for Christmas.” The boy was astounded. “You mean your brother gave it to you and it didn’t cost you nothing? Boy, I wish….” He hesitated. Of course Paul knew what he was going to wish for. He was going to wish he had a brother like that. But what the lad said jarred Paul all the way down to his heels.

“I wish,” the boy went on, “that I could be a brother like that.”

Paul looked at the boy in astonishment, then impulsively he added, “Would you like to take a ride in my automobile?”

“Oh yes, I’d love that.”

After a short ride, the boy turned and with his eyes aglow, said, “Mister, would you mind driving in front of my house?”

Paul smiled a little. He thought he knew what the lad wante d. He wanted to show his neighbors that he could ride home in a big automobile. But Paul was wrong again. “Will you stop where those two steps are?” the boy asked.

He ran up the steps. Then in a little while Paul heard him coming back, but he was not coming fast. He was carrying his little crippled brother. He sat him down on the bottom step, then sort of squeezed up against him and pointed to the car.

“There she is, Buddy, just like I told you upstairs. His brother gave it to him for Christmas and it didn’t cost him a cent. And some day I’m gonna give you one just like it…, then you can see for yourself all the pretty things in the Christmas windows that I’ve been trying to tell you about.”

Paul got out and lifted the lad to the front seat of his car. The shining-eyed older brother climbed in beside him and the three of them began a memorable holiday ride. That Christmas Eve, Paul learned what Jesus meant when he had said: “It is more blessed to give….”

1、The boy was astounded.

A、He was very surprised

B、He was so surprised that he was shocked

C、He was extremely surprised

D、The car was so beautiful that he felt excited

2、Paul looked at the boy…, then impulsively he added, “….”

A、 he did this without planning and thinking

B、he did this with careful thinking

C、he was impelled by his brother to do this

D、he was forced by his mother to do this

3、The boy was not coming fast because ().

A、he was coming down the steps

B、he wanted to sit down on the steps

C、he wanted to see the car clearly

D、he was carrying his crippled brother

4、He…squeezed up against him and pointed to the car.

A、moved closer and touched him

B、held him tightly in his arms

C、pushed him nearer to the car

D、pulled him closer and supported him

5、…the three of them began a memorable holiday ride.

A、easy to remember

B、likely to be noticeable

C、worth remembering

D、likely to be seen

当x→+0时，x-x²与x²-x³相比，哪一个是高阶无穷小？

若在区间(a，b)内函数f(x)的一阶导数f'(x)＞0，二阶导数f"(x)＞0，则f(x)在该区间内(  )

  A．单调递减、凹的  B．单调递减、凸的

  C．单调递增、凹的  D．单调递增、凸的

由直线y=0，y=x和x=1所围成的三角形薄片上的面密度为μ(x，y)=x，则该薄片的质量为(  )

  A．1 B．  C． D．