题目

一定温度下，某在物质水中的溶解度为S，计算该温度下这种饱和溶液中溶质的物质的量浓度，必不可少的物理量是 （） ①溶液中溶质的摩尔质量②溶液中溶质和溶剂的质量比③溶液的密度④溶液的体积． A . ①② B . ②③ C . ①③ D . ②④ 答案：C根据材料内容选择最佳答案。 Wanted  Are you hard-working? Do you like to meet people? If your answer is "Yes"; then we have a job for you as a waiter. Call AL Hotel at 5564779! Summer Job Do you like to talk with people? Do you like to write Stories? If you want to work for our magic as a  reporter, please call Karen at 5583366. Help Wanted Do you like babies? Can you look after a baby for two days? If you are sure to take good care of it, call Mr. Green at 7665898. $80 or more. Today! Be quick Cleaner wanted Can you make a large house clean and tidy? If you hope to get paid $20 once, call us this evening from 18:00 to 20:00. Our telephone number is 6338001. 1.If you want to be a       , you can call AL Hotel. A．waiter B．reporter C．cleaner D．driver 2.If you work as a cleaner every weekday, and once a day, how much will you be paid every week? A．$100. B．$150. C．$200. D．$240. 3.What is NOT mentioned in the ads? A．Jobs you can choose from. B．E—mail addresses. C．Telephone numbers. D．Time when you are supposed to work.