商品蛋鸡开产前饲养管理要点有什么？

有位同学用如图所示的装置来探究光的反射规律，竖直纸板可沿虚线折叠．

（1）如图甲，先让纸板在同一平面内，沿纸面射入一条光线EO，并找到反射光线OF，用量角器量出入射角和反射角的大小，反复实验比较两角的大小可得：反射角______入射角；

（2）将纸板如图乙折叠，______看到反射光线；（填“能”或“不能”）

（3）如果把甲图中的入射光EO移动到ON的右边，反射光OF就在ON的______；

（4）由以上实验我们可以得出光的反射规律有哪些？

①______；

②______；

③______．

阅读理解。

     A friend of mine named Paul received an expensive car from his brother as a Christmas present. On

Christmas Eve when Paul came out of his office, a street urchin (顽童) was walking around the shining

car. “Is this your car, Paul?"he asked.

     Paul answered, "Yes，my brother gave it to me for Christmas. "The boy was surprised. "You mean

your brother gave it to you and it didn't cost you anything?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 boy said surprised Paul greatly?

    "I wish, "the boy went on, "that I could be a brother like that. "Paul looked at the boy in surprise，then he said again, "Would you like to take a ride in my car?"

     "Oh yes, I'd love that. "

     After a short ride，the boy turned and with his eyes shining, said, "Paul, would you mind driving in

front of my house?"

     Paul smiled a little. He thought he knew what the boy wanted. He wanted to show" his neighbours that he could ride home in a big car. But Paul was wrong again. "Will you stop where those two steps are?"

the boy asked.

     He ran up to the steps. Then in a short while Paul heard him coming back, but he was not coming fast. He was carrying his little crippled(残疾)brother. He sat him down on the step 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 going to give you one just like it…then you can see for yourself all

the nice things in the Christmas windows that I've been trying to tell you about. "

     Paul got out and lifted the boy to the front seat of his car. The shining-eyed older brother climbed in

beside him and the three of them began an unforgettable holiday ride.

1. The street urchin was very surprised when _____.

A. Paul received an expensive car

B. Paul told him about the car

C. he saw the shining car

D. he was walking around the car

2. From the story we can see the urchin _____.

A. wished to give his brother a car

B. wanted Paul's brother to give him a car

C. wished he could have a brother like Paul's

D. wished Paul could be a brother like that

3. The urchin asked Paul to stop his car in front of his house _____.

A. to show his neighbours the big car

B. to show he had a rich friend

C. to let his brother ride in the car

D. to tell his brother about his wish

4. We can infer(推断)from the story that _____.

A. Paul couldn't understand the urchin

B. the urchin had a deep love for his brother

C. the urchin wished to have a rich brother

D. the urchin's wish came true in the end

5.The best name of the story is _____.

A. A Christmas Present

B. A Street Urchin

C. A Brother Like That

D. An Unforgettable Holiday Ride

修一条公路，已修长度和未修长度的比是1：5，又修了490米后，已修长度和未修长度的比是3：1，这时未修公路的长度为______米．

如果浮选柱选别过程中，精矿纯度低，可通过（）提高精矿纯度。

A、提高充气速度

B、如果冲洗水偏差率小于0.25cm/s，则提高冲洗水流量

C、如果液位过高，可以提高泡沫层厚度

一些重要的程序语言(如C语言和Pascal语言)允许过程的递归调用。而实现递归调用中的存储分配通常用

A) 栈
B) 堆
C) 数组
D) 链表