题目

某单质X能从某溶液中置换出单质Y,由此推断下列说法中正确的是 ( ) A.X是金属时,Y一定比X活泼 B.X可能是铁,Y一定是铜 C.X是金属时,Y可能是金属,也可能是非金属 D.X一定是排在金属活动性顺序中氢以前的金属 答案：选C。活泼金属只能置换出比它不活泼的金属,由题意知单质X能从某溶液中置换出单质Y,故X的活动性应比Y强;当X可能是铁时,Y的活泼性应比铁弱,可能是铜;当X是排在金属活动性顺序中H前面的金属时,Y可能是金属,也可能是非金属,如H2。When I was in the third grade, I was picked to be the princess（公主）in the school play. For weeks my mother had helped me practice my lines. But once on stage, every word disappeared from my head. Then my teacher told me she had written a narrator’s（解说者的）part for the play, and asked me to change roles. Though I didn’t tell my mother what had happened that day, she sensed my unhappiness and asked if I wanted to take a walk in the yard.It was a lovely spring day. We could see dandelions（蒲公英）popping(突然出现) through the grass in bunches, as if a painter had touched our landscape with bits of gold. I watched my mother carelessly bend down by one of the bunches. “I think I am going to dig up all these weeds,” she said. “From now on, we’ll have only roses in this garden.”“But I like dandelions,” I protested. “All flowers are beautiful-even dandelions!”My mother looked at me seriously. “Yes, every flower gives pleasure in its own way, doesn’t it?” She asked thoughtfully. I nodded. “And that is true of people, too,” she added.When I realized that she had guessed my pain, I started to cry and told her the truth.“But you will be a beautiful narrator,” she said, reminding me of how much I loved to read stories aloud to her.Over the next few weeks, with her continuous encouragement, I learned to take pride in the role. The big day finally came. A few minutes before the play, my teacher came over to me. “Your mother asked me to give this to you,” she said, handing me a dandelion. After the play, I took home the flower, laughing that I was perhaps the only person who would keep such a weed(野草).【1】he girl did not play the role of the princess mainly because .A. she felt nervous on the stageB. she lost her interest in that roleC. she preferred the role of the narratorD. she had difficulty memorizing her words【2】Why did the mother suggest a walk in the garden?A. To remove the dandelions.B. To enjoy the garden scene.C. To have a talk with her daughter.D. To help her daughter recite the words.【3】. What is the main idea of the story?A. Everybody can find his or her own way to success.B. Everybody has his or her own value in the world.C. Everybody should learn to play different roles.D. Everybody has some unforgettable memory.