题目

农民在给水稻幼苗施肥时，若一次性施肥过多，会造成水稻幼苗枯萎，甚至死亡，其主要原因是A. 土壤溶液浓度过高，幼苗根毛细胞失水B. 土壤溶液浓度过高，幼苗根毛细胞吸水C. 土壤溶液浓度过低，幼苗根毛细胞失水D. 土壤溶液浓度过低，幼苗根毛细胞吸水 答案：【答案】A【解析】试题分析：植物细胞吸水和失水的原理是细胞外部溶液的浓度大于细胞内部浓度时失水，细胞外部溶液的浓度小于细胞内部浓度时吸水。一次施肥过多，会使土壤溶液浓度过高，大于植物细胞溶液的浓度，植物细胞失水，导致植物因失水而萎蔫。     When a storm is coming, most people leave the area as quickly ad possible and head for safety. But there are a few people who will get into their cars and go straight for the center of the storm. These people are willing to risk(冒…危险)being killed by floods or 100-kilometer-an-hour winds for the excitement of watching the storm close up.    “Storm chasing(追逐)” is becoming an increasingly popular hobby(喜好), especially in the Midwest of the United States, where there are frequent storms between March and July. A storm chaser begins the day by checking the Internet for the latest weather reports, and then drives up to 1,000 kilometers to where the storm will be and waits for it to develop.     Although anyone can do it , storm chasing is extremely dangerous. The power of a big storm can throw a cow into the air or destroy a whole house in seconds. Storm chasers are also often hurt in accidents caused by driving in a heavy rain. If you are a beginner, it is much safer to join a group for storm-chasing vacations during the storm season. Even then, storm chasing is not all adventure and excitement . “Storm chasing is 95% driving,” says Daniel Lynch, who spends most of his summer storm-chasing.    “Sometimes you can sit around for hours waiting for something to happen, and all you get is blue sky and a few light showers.”     However, for storm chasers, it is all worth it. “When you get close to a storm, it is the most exciting sight you will ever see in your life,” says Jasper Morley. “Every storm is an example of the power of nature, It is the greatest show on Earth.” 56. For storm chasing, the first thing storm chasers do is to          . A. head straight for the center of the storm  B. get into the car for safety C. wait patiently for the storm to develop    D. collect information about a coming storm 57. Beginners of storm chasing are advised             . A. not to drive in a heavy rain                           B. to do it in an organized way C. not to get too close to a storm                 D. to spend more time on it in summer 58. By saying “it is all worth it” in the last paragraph, the author means that             . A. storm chasing costs a lot of money          B. storm chasing is worth hours of waiting C. efforts in storm chasing are well paid          D. a storm presents the greatest show on Earth 59. What can we learn from the text? A.  Sometimes storm chasers get nothing but disappointment B.  Many storm chasers get killed in the storms. C. Storm chasing is becoming popular around the world. D. Storm chasing is only fit for young people.