题干

两种气态烃组成的混合气体,完全燃烧后得到CO2和H2O的物质的量随着混合烃物质的量的变化如图所示,则下列对混合烃的判断正确的是(   )

①可能有C2H4 ②一定没有C2H6 ③一定有C3H8

④一定有CH4⑤可能有C2H6 ⑥可能有C2H2

A:②⑤⑥

B:④⑥

C:①②④

D:②③

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答案(点此获取答案解析)

C

同类题3

阅读下面短文,从短文后各题所给四个选项(A、B、C和D)中,选出可以填入空白处的最佳选项,并在答题卡上将该项涂黑

    Many people think that babysitting is one of the1jobs for young people. They imagine a teenager putting a few well-behaved children to bed and then continuing to watch television until the parents return home to hand over some money. Well, I can tell you how2that thought is.

    I now work all3on Wednesdays for a Ukrainian family with three young boys. In the early morning, I go there to 4the older two while their mother does her jobs or takes care of her six-month-old baby. However, I am also there to5their English by teaching them songs and games in my native language.

    Now, four months later, I get home at the end of the day6exhausted!Babysitting is not a job for the7or the weak. I expected8children who would behave well and listen to me all the time. 9,I don't think those kind of children exist at all. While my two boys are usually polite and calm, they are10children and also like to fight, scream and lose their temper for no real11. I often have no idea why they cry together.

    Being a babysitter requires you to play a hundred different12throughout the day. I have to be a friend when I play with the boys, but their 13when I tell them to do something. When they hurt themselves, I have to be their14, and when they fight over15 things like sharing their crayons(彩笔),I have to be a negotiator(调停者)。 When lunchtime rolls around, I am a(n) 16to prepare the meal and then a maid as I clean up after lunch. Finally, in English, if someone is very17, we say they have the “Patience of God”. I think I embody(体现) this 18sometimes!

    Despite the19involved in my job, I usually do enjoy it. Working with children is so tiring that I always feel20after leaving them with their parents at the end of the day!