题目: 据报道,1995年化学家合成了一种化学式为C200H200含多个—C≡C—的链状烃,则分子中含有碳-碳叁键数最多可以是:A.49B.50C.51D.100 答案: 答案:B烷烃分子中去掉4个氢原子即得到1个碳碳三键,即每少4个氢原子,即有1个碳碳三键。因为……2,所以答案选B。
题型:阅读理解 阅读理解。 Henry was a carpenter(木匠)of our village. Once I asked him to make a dining table for my wife. He made it just the right size to fill the space between the two windows. When I arrived home that evening, Henry was drinking a cup of tea and writing out his bill for his work.. My wife said to me,quietly,"That,s his ninth cup of tea today."But she said loudly, "It's a beautiful table,dear,isn't it?" "I won't decide about that until I see that bill." I said. Henry laughed and gave me his bill for the work. It said: BILL One dining table June 10,1995Cost of wood 17.00Paint(油漆) 1.50Work,8 hours(1 an hour) 8.00Total(总计) 36.50 When I was looking at the bill,Henry said,"it's been a fine day,hasn't it? Quite sunny." "Yes,"I said. "I'm glad it is only the 10th of June." "Me too,", said Henry. "You wait一it'll be a bit hotter by the end of the month." "Yes. Hotter一and more expensive. Dining tables will be 20 more expensive on June 30th,won't they,Henry?" Henry looked hard at me for half a minute. There was a little smile in his two blue eyes. I gave his bill back to him. "If it isn't too much trouble,Henry,"I said,"Please add it up again. You can forget the date." I paid him 26. 50 and he was happy to get it.1. Why did Henry talk about weather when the writer was looking at the bill? A. Because it was a fine day indeed, B. Because he wanted the writer to look at the bill carefully. C. Because he wanted to tell the writer what the weather was like.D. Because he didn't want the writer to go through the bill carefully.2. Why did the writer say that dining tables would be 20 more expensive by the end of June?A. Because he thought Henry would almost certainly add the date to the cost of the dining table. B. Because it was difficult to make dining tables in hot weather.C. Because paint would be more expensive.D. Because the cost of wood would be more expensive.3. The writer thought Henry would ask for______if he made a dining table on the last day of June.A.26.50 B. 56. 50 C. 46.50 D. 20.004.When the writer gave him the money,Henry was happy because_______. A. he got the money easily B. be didn,t have to add up the cost againC. he got what he should get for his work D. he got much money for his work5. From the story we know that_______.A. Henry had written out the bill before the writer got homeB. Henry still wanted to get 36. 50 for his work in the endC: Henry made a mistake in the billD. Henry tried to get more money for his work 查看答案
题型:单项选择题 A1/A2型题 男性,4岁,在独自游戏时突然出现呼吸困难,吸气时胸骨上窝、锁骨上窝和肋间隙明显凹陷,其病因最可能是().A.急性上呼吸道感染B.自发性气胸C.支气管哮喘D.气管异物E.脑外伤 查看答案
题型:选择题 下列有关分散系的说法正确的是A.一种分散系中可以有一种分散质,也可以有多种分散质B.浊液的分散质都能通过过滤从分散剂中分离出来C.分散剂一定是液体D.同一种溶质的饱和溶液要比不饱和溶液的浓度大 查看答案