通常人体所能承受的安全电压为（）。A、36V B、40V C、45V D、50V

碘被称为“智力元素”，科学合理地补充碘可防止碘缺乏病．碘酸钾(KIO₃)是国家规定的食盐加碘剂，它的晶体为白色，可溶于水．碘酸钾在酸性介质中与过氧化氢或碘化物作用均生成单质碘．以碘为原料，通过电解制备碘酸钾的实验装置如图所示．请回答下列问题：

(1)碘是________(填颜色)固体物质，实验室常用________方法来分离提纯含有少量杂质的固体碘．

(2)电解前，先将一定量的精制碘溶于过量氢氧化钾溶液，溶解时发生反应：3I₂＋6KOH===5KI＋KIO₃＋3H₂O，将该溶液加入阳极区．另将氢氧化钾溶液加入阴极区，电解槽用水冷却．电解时，阳极上发生反应的电极反应式为________；阴极上观察到的实验现象是_____________________________．

(3)电解过程中，为确定电解是否完成，需检验电解液中是否有I^－.请设计一个检验电解液中是否有I^－的实验方案，并按要求填写下表．要求：所需药品只能从下列试剂中选择，实验仪器及相关用品自选．试剂：淀粉溶液、碘化钾淀粉试纸、过氧化氢溶液、稀硫酸.

(4)电解完毕，从电解液中得到碘酸钾晶体的实验过程如下

步骤②的操作名称是________，步骤⑤的操作名称是________．步骤④洗涤晶体的目的是________________________________________________________________________．

Several years ago, I worked as a truck driver for a company. On Saturdays I usually spent several hours doing something to keep my truck in good condition.

One Saturday, as I was cleaning my truck, I noticed the boss’s elderly father came out to ask his grandson to take him fishing after work. The grandson told him all about how much he would love to do that, but he just couldn’t because he had other plans already. The old man hobbled (蹒跚) off to the house.

Then I heard the grandson telling his dad, "I’m not taking that old man fishing! It’s worse than taking a kid."

That just broke my heart.

I quit working immediately and went home to fetch my fishing gear (渔具) and a chair. Then I came back and invited the old man to go fishing. He accepted happily.

When we got to the river, I let him sit in the chair at the edge of the water. It wasn’t long before he got a fish. He got one fish after another. His eyes were shining like a child. About half an hour later, he told me he was tired and needed to go home. So I took him and the fish home.

Two weeks later, the old man died. His family told me later that all he talked about during that time was his fishing trip. I am satisfied that I have taken an old man on his last fishing trip, but I am sorry that his family have lost their last chance. Whenever you get the chance, don’t forget about taking Grandpa fishing. Someday, you may be in the same place and you’ll want your family to care about you, too.

小题1:The writer wrote the passage mainly to ________.

A．tell us something about his work

B．tell us about a fishing experience

C．persuade us to take Grandpa fishing

D．persuade us to care about the elderly小题2:The old man’s Grandson refused to fish with him because ______.

A．he had something more important to do that day

B．he didn’t like to fish with an old man

C．he was tired of his job and he wanted to rest

D．he preferred fishing with a child小题3:What’s the possible meaning of the underlined word "quit"?

A．start

B．stop

C．imagine

D．try小题4:According to the passage, we can infer（推断） that the author is _______.

A．willing to make his boss happy

B．in need of care from his family

C．prefers fishing to his work

D．kind and warm-hearted

资产负债率，对其正确的评价有( )。

A．从债权人角度看，负债比率越大越好

B．从债权人角度看，负债比率越小越好

C．从股东角度看，负债比率越高越好

D．从股东角度看，负债比率越低越好

植物激素脱落酸具有促进植物叶片和成熟果实脱落，促进种子休眠等生理作用。乙烯是另一种植物激素，它除了具有促进果实成熟的作用外，也能够促进植物叶片和果实的脱落。某兴趣小组的同学想通过设计一个实验方案，探究乙烯和脱落酸促进植物叶片脱落的差异。所选择和使用的材料和用具有：生活状态相同的同种植物若干株，适宜浓度的脱落酸和乙烯利（一种乙烯释放剂），蒸馏水及所需的相关器材和用具。请你协助他们设计完成这一实验，预测实验结果，得出相应结论。

实验原理：使用适宜浓度的（）处理植物叶片后，可以缩短植物叶片脱落的时间。

火灾的危害（）

A.毁坏财物

B.残害人类生命

C.破坏生态平衡

D.引起不良的社会和政治影响