我国的新（饮用天然矿泉水国家标准）规定了饮用水中可能致癌物溴酸盐的限值：0.01mg/L，日前很多饮用水企业都采用臭氧消毒法进行水的消毒，这个过程可能生成溴酸盐。原因是水中的Br－被臭氧氧化为BrO2-，其过程示意为：Br－
BrO－ BrO2- BrO3-，下列有关说法正确的是
A．臭氧消毒法和明矾净水原理相同，都是利用胶体吸附原理
B．若改用氧气消毒，可避免生成溴酸盐
C．BrO- 3氧化性比O3强
D．生成溴酸盐的过程是给水消毒的副反应，需控制条件减少BrO3-的产生
答案：D
题目分析：A、臭氧消毒利用了臭氧的强氧化性，而明矾净水则利用胶体的吸附作用，两者原理不同，错误；B、氧气不能用于消毒，错误；C、BrO3-是由O3氧化生成的，故氧化性比O3弱，错误；D、溴酸盐是可能致癌物，正确。
Directions: There are 4 passages in this part. Each of the passages is followed by 5 questions or unfinished statements. For each of them there are 4 choices marked A, B, C and D. Choose the best one.
Passage One
| American consumers like convenience very much. During the last 50 years, there has been a dramatic increase in such labor-saving devices as automatic washing machines, clothes dryers, dishwashers, food processors, microwave ovens, garbage disposals and power lawn mowers. Today, all of these and many more, are found in a typical suburban home. These labor-saving devices are designed to reduce the time spent on housework. However, the time that Americans save is quickly spent on other activities. The American desire for convenience also created the concept of fast-food restaurants, found in every city and almost every small town in the United States, and now exported all over the world. These fast-food restaurants, such as McDonald’s and KFC, serve sandwiches, salads, fried chicken, seafood, and other food to hurried customers in five minutes or less, often at a drive-up window. There are also a wide variety of restaurants that will deliver Chinese food, pizza, and other dishes to people’s homes in about a half-hour. In many areas there are "take-out taxis" that will deliver food from the menus of 20 or 30 different restaurants for a small charge. For those who prefer to prepare their food at home, American grocery stores are full of convenience foods that are packaged and ready to cook or even precooked. Like microwave ovens and dishwashers, fast-food and take-out restaurants are convenient because they save the American consumer time that would otherwise be spent fixing meals or cleaning up. More than half of all the women in the United States are currently employed. This includes mothers with children under the age of 18. More than half the women with little children under the age of six hold jobs. Sixty-eight percent of the women who have school-age children are employed. Families with working mothers need all the time-savers they can get. Thus, the conveniences that Americans desire reflect not so much a leisurely lifestyle as a busy lifestyle in which even minutes of time are too valuable to be wasted. Alexis de Tocqueville was one of the first to see in this a curious paradox (自相矛盾) in the American character. He observed that Americans were so busy working to acquire comforts and conveniences that they were unable to relax and to enjoy leisure time when they had it. Today, many Americans have what one medical doctor has called "the hurry sickness". |
Americans like fast food and takeout restaurants because ______.
A．they are cheap
B．they offer nutritious and tasty food
C．they provide superior service
D．they are convenient