某工厂有一大型储水罐供全厂生产用水，已知每天晚8点至早8点蓄水，蓄水管流量为8吨/小

造成卡环和支托折断的原因是()

A．卡环材料性能差

B．弯制过程中反复弯曲次数过多，使钢丝的性能遭到破坏

C．支托凹和卡环间隙预备不够

D．患者使用不当

E．铸造卡环内存在铸造缺陷

阅读理解。

     Most supermarkets in China provided free plastic bags. It was convenient for people to do shopping,

but things changed. To protect the environment, supermarkets all over China stopped providing free plastic

bags from June 1, 2008.  If you don't want to pay money to buy them, you'll have to bring your own

shopping bags.

     What can we use to hold things we buy from shops? Students at Qing-shan Middle School had some

good ideas. One idea was making different kinds of eco-shopping bags. 54 students at that school made their

own eco-shopping bags. They held an eco-shopping bag show last Friday afternoon. Many students made the

bags with used clothes. They painted pictures like the Olympic rings on them. Some bags were made of used

materials like used paper, old newspapers. Some were made of eco-materials like bamboo.

     A boy student, Wang Lin, made his bag with several old newspapers. We asked him whether the bag was

strong enough. Wang Lin said it was."No problem. I took six bottles of water in the bag from the shop to my

home yesterday evening," he said."I think it's strong enough to hold even ten bottles of water."

     Fang Yuanyuan, a girl student, had a more traditional way to make her bag-a bamboo basket."It was a

hard job," she said. "With my grandfather's help, I spent a whole afternoon making it."

     The students also asked their parents and friends to use eco-shopping bags instead of plastic ones. Next

Saturday afternoon, the school will hold another eco-shopping bag show to help shops and stores get ideas

from the students' work.

1. The supermarkets all over China stopped providing _________ from June 1, 2008.

A. eco-shopping bags

B. plastic baskets

C. free plastic bags

D. bamboo baskets

2. Wang Lin made his bag with _________.

A. bamboo

B. used clothes

C. plastic

D. old newspapers

3. Why will the school hold another eco-shopping bag show?

A. To know if the bag was strong enough.

B. To show their pictures on the bags.

C. To make money by selling them.

D. To give ideas to shops and stores.

4. What is the main idea of the passage?

A. People can still use plastic bags.

B. Students encourage people to use eco-shopping bags.

C. Students have good ideas to make money.

D. Most supermarkets will go on providing free plastic bags.

如果关于x的方程x²+4x-m=0有两个不相等的实数根，那么m的取值范围是______．

“黑箱”“白箱”“灰箱”划分的标准是（）

定位是水下地形测量的一个重要组成部分，可根据离岸距离的远近采用不同的定位方法。下列主要方法中，可以离岸工作距离最远的是( )。

A．光学仪器测角定位
B．无线电定位
C．电子全站仪定位
D．GPS定位