孔子说：“学而时习之，不亦悦乎？”这句话是强调的重要性[ ] A、预习 B、听讲

Linda and Betty were both twenty years old. They studied in the same medical college. In June, after a school year was over, they decided to take a vacation in the country. They went to several towns and villages, and visited some places of interest, saw and heard a lot of interesting things. They enjoyed themselves very much.

One afternoon, they were going to stay overnight in a small town. It was too hot to go further and they wished they could find a river and swim in the cool water. They were driving the car slowly while they were looking around. Suddenly Linda saw a lake not far away. They drove there fast and stopped the car by the lake. They looked around and found a man was sitting on a stone and fishing there. When they took their clothes and were going to jump into the water, the man came up to them and shouted," Sorry, Madams' swimming is not allowed (允许)in the lake!"

"Why didn't you tell us about it before we took off our clothes?" Betty said angrily. "But it isn’t forbidden to take off clothes by the lake," said the man.

小题1:Linda and Betty were       .

A．classmates

B．sisters

C．doctors

D．nurses小题2:The man didn’t want them      .

A．to fish in the lake

B．to swim in the lake

C．to take off their clothed

D．to get angry小题3:The word "forbidden" means_____.

A．支持

B．禁止

C．同意

D．干扰

中科大陈乾旺教授等人发现了人工合成金刚石的新方法，其化学原理为：

（1）8Na+6CO₂

一定条件

C（金刚石）+C（石墨）+4Na₂CO₃

该法比1955年人工首次制得金刚石的方法容易得多，其化学原理是：

（2）C（石墨）

1800℃1.2×1010Pa

C（金刚石）

以下有关表述中正确的是（　　）

A．新法（1）利用的是化学变化，旧法（2）利用的是物理变化

B．在反应（1）中，利用了金属钠的还原性

C．在反应（1）中每生成12g金刚石需要消耗23g金属钠

D．在反应（1）和（2）中，金刚石都是还原产物

已知x-y=4，xy=12，则x²+y²的值为（　　）

A．28

B．40

C．26

D．25

垄断在经济生活中占统治地位，是进入（）最重要的经济特征。

事故应急处理管理制度规定安全管理领导小组成员不少于（）名。

A.1

B.2

C.5

D.10