下列哪种荧光染料在酸性溶液中荧光强度显著降低A．FITC(异硫氰酸荧光素) B．PE

阅读理解。

     There was an old pear tree in a man's garden. In the past,  the  tree  fruited  every  year, so the man

would  get  many  pears. But  now, the tree got old. There  were  no more  pears  for  the man. So the

ungrateful man decided to cut the tree down. When he walked toward the tree with an axe in his hand,

the tree said to him, "Please don't cut me down. I have borne so many pears for you in the past years.

Now I will die soon. I only have a short time to live. Please don't kill a dying tree that has done so much

for you."

     "I'm sorry. I have to do so," the man said, "because I need wood to make a chair." Then he began to

wave his axe. At that moment, a bird in the old tree shouted at him, "Don't cut it down! Every time you

go out and your wife feels lonely, she will come out to the garden and sit under the tree to enjoy its cool

shade, and I sing songs to make her happy. We give much pleasure to  your  wife  when  you  are away

from home."

     The man didn't listen to the bird and drove it away. Just when he was about to cut the tree, some

bees flew out of it and said, "Listen! If you agree not to kill this tree, we will give you delicious honey

every day. Would you please leave the tree with us?"

     The man got moved. He said, "You are so kind to the tree, although it has become old. Now I see

that I shouldn't cut it down. It has done so much for me and my wife. Let the tree stay here, and let the

bird continue its songs here." With these words, the man left. And the old tree lived there to its last day.

1. Which can be the best title of the story?

A. The Singing Bird          

B. The Man's Wife

C. The Old Tree            

D. The King Bees

2. The most important reason for the man to cut down the tree isn't that the man couldn't get any pears

from it, is it?

A. No, it isn't.                          

B. Yes, it isn't.

C. No, it is.                            

D. Yes, it is.

3. What made his wife happy when the man was not at home?

A. The tree and its shade.            

B. The tree and the bird.

C. The bird and its songs.            

D. The bees and their honey.

4. In the story, the underlined word "continue" means ______.

A. start                            

B. go on

C. take                            

D. speak again

5. What can we learn from the story?

A. People should never be ungrateful.            

B. Good wood comes from pear trees.

C. Old people are kind and friendly.            

D. Birds and bees are always helpful.

是银锌碱性电池的正极活性物质，可通过下列方法制备：在加入适量 溶液,生成沉淀，保持反应温度为80，边搅拌边将一定量溶液缓慢加到上述混合物中，反应完全后，过滤、洗剂、真空干燥得到固体样品。反应方程式为

回答下列问题：

（1）上述制备过程中，检验洗剂是否完全的方法是      .

(2)银锌碱性电池的电解质溶液为溶液，电池放电时正极的 转化为，负极的转化为，写出该电池反应方程式：                            .

(3)准确称取上述制备的样品（设仅含和）2.558g，在一定的条件下完全分解为 和 ，得到224.0mL（标准状况下）。计算样品中的质量分数（计算结果精确到小数点后两位）。

二尖瓣狭窄患者可听到的最重要的杂音是（）

A.心尖区收缩期吹风样杂音

B.心尖区舒张期隆隆样杂音

C.主动脉瓣区舒张期叹气样杂音

D.肺动脉瓣区舒张期吹风样杂音

E.胸骨右缘第2肋间响亮而粗糙的双期杂音

对于病理性赌博的成因，生物学的解释是人脑内的（）分泌异常。

无线调车机车信号和监控系统具有记录处理功能，但不具有系统管理功能。