题目

关于“观察紫色洋葱鳞片叶外表皮细胞的质壁分离和复原”实验的叙述中，正确的是A. 原生质层的伸缩性和通透性均大于细胞壁B. 随着质壁分离的进行，液泡的颜色变浅C. 用无水乙醇处理表皮细胞，质壁分离现象更明显D. 实验过程中，至少需要对装片进行三次观察 答案：【答案】D【解析】原生质层具有选择透过性，细胞壁是全透性的；原生质层的伸缩性大于细胞壁的伸缩性；当外界溶液浓度大于细胞液浓度时，细胞失水，出现质壁分离现象，反之则细胞吸水，引起质壁分离复原。无水乙醇对细胞有毒害作用，会导致细胞死亡；死亡的细胞不会发生质壁分离。A、原生26、Have you ever stayed in a hotel? Most Chinese hotels often provide people with things like disposable（一次性的）toothbrushes，toothpaste，shampoo and so on．Many people like the idea because they don’t have to bring their own．But，if you travel to Beijing，remember to bring your own things．Starting from June，some hotels’ in Beijing no longer provide people with these disposables．They want to ask people to use fewer disposable things。 Many disposable things are made of plastic（塑料）．People throw them away after only using them once．It is a waste of natural resources（资源）and is very bad for the environment．Do you know，one Chinese person makes as much as 400 kg of waste a year! Most of that waste comes from disposable things．In Beijing，people throw away about 19 000 000 kg of plastic bags and l 320 000 kg of plastic lunch bowls every year! Plastic can take between 100 and 400 years to break down（腐烂）．So the less plastic we throw out，the better．Wherever you travel，bring your own things and use them again and again． 根据短文内容，填空或回答问题。 1．Many people like disposable things because they don’t have to_______ _____ _____ 2. Starting from June，some hotels in Beijing no longer_____ people_____ these disposables． 3．It is a _____of natural resources and is very bad for the_____． 4．How much waste does one Chinese person make one year? _____________________________________________ 5．What should we do to protect our environment? _____________________________________________