绘图题：请画出光电管隔离电路图。

阅读理解。

     Most animals protect (保护) their young until they are old enough to take care of themselves. A fish

that swims in the rivers of South America protects its young in a very strange way. This fish, a kind of

catfish, uses its mouth to keep its babies from danger.

     When this catfish lays (产下) its eggs, it carries them in its mouth. From what we know, it does not

eat during this time. After the eggs hatch (孵化), the fish swims with its young to protect them. It opens

its mouth when danger appears and its young swim inside. They swim out only when it is safe again.

     These catfish may have a peculiar way to protect their young, but it seems (似乎) to work.

1. The best title (标题) for this passage is ________.

A. Fish in South America  

B. How A Fish Protects Its Young

C. Laying Eggs      

D. A Cat That Swims

2. We can guess the young fish are ________.

A. very brave          

B. large

C. yellow and gold    

D. small

3. If the young fish were not near their mothers, they would be________.

A. in greater danger  

B. sadder

C. happier        

D. safer

4. The word "peculiar" in the last line means________.

A. easy        

B. strange

C. useless        

D. dangerous

确定正数A的最小值与负数B的最大值，使得不等式

在区域D=(x，y)|x＞0，y＞0内成立．

趋势线被突破后，这说明（）。

A.股价上升

B.股价走势将反转

C.股价走势将加速

D.股价会下跌

在新材料应用方案的选择过程中，通常把( )作为主要评价原则。

A．技术先进

B．技术适用

C．技术可靠

D．经济合理

真空槽移至处理位后用顶枪烘烤，可以（）。

A.烘烤时间在1小时以上

B.增大焦气流量

C.补偿温度损失

D.强化槽底的热负荷

E.减少焦气流量