现有物质：①二氧化碳②一氧化碳③熟石灰④金刚石⑤高锰酸钾请按要求填写化学式：
（1）能产生温室效应的气体：______ （2）天然存在的最硬物质______
（3）用于降低土壤酸性的碱______ （4）有毒气体______
（5）可用于制氧气的暗紫色固体______．
（1）能产生温室效应的气体是二氧化碳，化学式是CO2；
（2）天然存在的最硬物质是金刚石，化学式是：C；
（3）用于降低土壤酸性的碱是熟石灰，化学式是：Ca（OH）2；
（4）有毒气体是一氧化碳，化学式是：CO；
（5）可用于制氧气的暗紫色固体是高锰酸钾，化学式是：KMn04．
故答为：（1）CO2；（2）C；（3）Ca（OH）2；（4）CO；（5）KMn04．
| Recently, I flew to Las Vegas to attend a meeting. As we were about to arrive, the pilot announced with apology that there would be a slight (16) before setting down. High desert winds had (17) the airport to close all but one runway. He said that we would be (18) the city for a few minutes waiting to (19) . We were also told to remain in our seats meanwhile with our seat belts fastened (20) there might be a few bumps(颠簸). Well, that few minutes turned into about four-five minutes, including a ride that would make a roller coaster(过山车) (21) by comparison. The movement was so fierce that several passengers felt (22) and had to use airsickness bags. As you might guess, that’ s not a good thing to have happen in a(n) (23) space because it only (24) to increase the discomfort of the situation. About twenty minutes into the adventure, the entire airplane became very (25) There was now a sense of anxiety and fear that could be (26) noticed. Every passenger simply held on for dear life …except one. A (27) was having a good time！ With each bump of the (28) , he would let out a giggle (咯咯地笑)of delight. As I observed this, I (29) that he didn’t know he was supposed to be afraid and worried about his (30) . He neither thought about the past nor about the future. Those are what we gown--ups have learned from (31) . He was (32) the ride because he had not yet been taught to fear it. Having understood this, I took a deep breath and (33) back into my seat, pretending I was (34) on a roller coaster. I smiled for the rest of the flight. I even (35) to giggle once or twice, much to the chagrin(随恼) of the man sitting next to me holding the airsickness bag. |
The passage starts with an elephant story in order to explain that in India ______.
A．people easily fall victim to elephants’ attacks
B．the man-elephant relationship is getting worse
C．elephant tamers are in short supply
D．dogs are as powerful as elephants