题目内容

【题目】下列关于机化合物的说法确的是( )

A乙烯分中含碳碳双键 B以淀粉为原料制取乙酸乙

C丁烷有3种同分异构体 D油脂的皂化反应属于加成反应

【答案】B

【解析】A乙烯分子是以氯乙烯为原料,通过分子之间的特殊的加成反应——加聚反应形成,发生加聚反应后分子碳原子变为饱和碳原子,不再含碳碳双键,错误B.淀粉是多糖,水解产生葡萄糖,葡萄糖在酒化酶的作用下反应产生乙醇;乙醇催化氧化产生乙醛,乙醛在进一步氧化产生乙酸。乙酸与乙醇在加热和浓硫酸存在时发生酯化反应形成乙酸乙酯和水。因此以淀粉为原料制取乙酸乙酯,正确C.丁烷有正丁烷和异丁烷种同分异构体,错误D.油脂的皂化反应属于取代反应,错误。

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【题目】A

阅读下短文,从每题所给的A、B、C、D四个选项中,选出最佳答案。

Driving on up to Yosemite with my family was exciting but nerve-racking (神经紧张的). I had never been to such an amazing national park before, yet I wasn’t the most athletic person so I knew that I couldn’t stick through all the hiking up and down. It actually ended up being a fun and adventurous experience.

The ride there was definitely long but worth it. As I woke up from my nap, I saw the beautiful scenery of the tall mountains and beautiful streams. The trails were made nicely for visitors. The waterfalls were breathtaking. Climbing up rocks was one of my favorite parts. Even though I fell a couple of times, I still have a lot of fun. The fact that my family and I spent so much time together all trying to find out which route to take and what views to watch really brought us closer together.

The great thing about nature is that, it’s just you, the views, and the people around you. There’s nothing there to bother you and it’s the best way to relax and enjoy yourself. Yosemite has 5 of the world’s highest waterfalls, and about 300 lakes. The structure of each mountain is incredible; it’s formed in ways that almost take your breath away. Some of them are of a deep dark color with waterfalls forming; some are formed with spots of green peeking (窥探) out. It’s definitely something you wouldn’t want to miss.

Yosemite isn’t the only great National Park but based on my experience I highly recommend going out and enjoying nature with family and friends. It’s a great time to bond, laugh, and take in what Mother Nature offers.

【】The author writes the first paragraph mainly to _____.

A. introduce the topic of this passage

B. offer an example to us

C. tell us his future plan for hiking

D. describe a national park

【】While climbing up rocks, the author was _____.

A. nerve-racking B. injured

C. pleased D. worried

【】According to the passage, Yosemite _____.

A.is crowded with visitors every day

B.is the only great National Park

C.is worth travelling to

D.is nothing but a common destination

【】The author suggests us _____.

A. keeping a good bond with other people

B. visiting Yosemite now and then

C. trying to protect the environment

D. going out to enjoy the beauty of nature

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