过敏性反应的特点是（）.
A.属于迟发作用
B.通常需要多次接触低剂量的不同化学物
C.一次接触大剂量的单一化学物也可引起反应
D.具有明显的剂量-反应关系
E.呈现出多种多样的损害表现
参考答案：E
解析：过敏反应时由于机体接触化学物后引起体内淋巴细胞致敏，再次接触后出现的一种变态反应。过敏反应又分为四型，即速发型反应、细胞毒型反应、免疫复合物型反应和迟发型反应。反应的表现多种多样，有呼吸道体征、消化道体征、皮肤局部表现、溶血、肾炎等。该损伤的效应不具有剂量反应关系，而主要是个体因素决定反应的强弱。故正确答案为E。
根据短文内容,从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。 You slowly open your eyes. Ah, another beautiful morning. You think to yourself, "It's great not to have anything to worry about". OH NO! Today is exam day and you haven’t studied enough! 小题1: How can you deal with the mountains of stress that exams seem to create? Read on to find out some useful study tips to prepare for exams: Get into a routine If you get started early enough before your exams, you will find you don’t need to put in any all-nighters. Find the time of the day that you study the best. Pick a couple of hours and stick to this study time. Get to know how you learn the best. 小题2: Plan ahead Planning ahead is the best way to maximize your chances of good grades. You may have only limited time to study. 小题3: Ask your teachers to help you make a list of the most important topics to study. If you stick to a schedule, it will start to seem manageable. Look after yourself Fresh fruit and vegetables will give you reserves of energy and increase your ability to concentrate. Don't stay awake all night trying to study. Wind down after study and try some relaxation exercises. Having regular exercise will keep your mind active. 小题4: Assistance and resources Your teachers will usually be more than happy to meet with you outside of class times. Make appointments to meet with them regularly. Don't waste their time, however. Plan what you want to discuss and have some questions written down. 小题5: Practise on past exam papers, but don't rely only on them. There is no such thing as a short cut when it comes to exams.
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