题干

集气瓶被誉为“万能瓶”,如下图装置是其中的一种.当被收集的气体从a口进入时,瓶内空气从b口排出,相当于向上排空气法收集气体.现若将被收集的气体从b口进入,则它可收集的气体为:①H2②CH4③CO2(   )

A:只有①

B:只有①和②

C:只有③

D:①②③均可

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B

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    I loved my aunt Suzy. She was such a kind old lady. I loved going to her house on holiday. She had been sick for the last few years and, though my job had taken me away across the town, I tried to visit her as much as possible. I helped with the shopping, the cooking and the cleaning and taking her pet cat Mazy to the vet.

    Sad as her passing away was, what happened to Mazy was even more worrying. Because aunt Suzy had no children, there wasn't anyone who seemed to care for her beloved cat friend. I would have taken her in a short time, but my apartment doesn't allow pets. First, we talked with her neighbors. Mr. Jenkins, who was alone and lived across the street, wasn't interested. Joe and Sally who lived next door had a small child with serious skin allergies(过敏症). My aunt's best friend Molly who had lived just down the road was unable to take care of herself as she had serious health problems.

    Second, we thought about our family members. My brother Bobby and his wife Jill were eliminated at once as they aren't cat people. My cousin in California was a bit interested, but we weren't sure about the trip as Mazy was nearly as old as my aunt (in cat years!). Finally, we came to the local humane society to see whether they would be able to help her find a new home. The problem was that most people and families only welcomed a smart little cat into their home, not a dull old one.

    In the end, we had to put Mazy to sleep. I had spoken with the vet and realized it was possible for the best. It was so hard to lose aunt Suzy and then have nowhere for Mazy to live. A few months went by and I had gone to my aunt's house to clear out some of her belongings. I happened to see her mailman. Jerry and we started to talk about my aunt when he asked about Mazy. I told him that we had to put Mazy to sleep because we couldn't find a home for her. Jerry got really quiet. “I promised Suzy that if anything ever happened to her, I'd take care of Mazy”, he said sadly. “Suzy always said she'd told her lawyer the arrangement.”

    Hearing this, my heart sank to my feet and I almost cried. The saddest part, I realized, was this all could have been avoided. I guess we were just so busy in those final months that we didn't think about it. We could have called my aunt's lawyer to take care of it in less than 10 minutes. I'll never forgive myself for not thinking of it sooner. And I'll never forgive myself for losing Mazy.