题目

Many people say that they are working too many hours. They don't have enough time to relax or to stay with their family.Work hours are different from one country to another. In France，people spend about 1 646 hours a year at work. In Japan，however，people work about 2 519 hours a year. That means a Japanese worker works 513 more hours a year than a French worker.Why do people work so many hours？Some people work extra hours because they want to make more money. However，many companies don't pay overtime. Their workers don't get more pay for more work. Some people think it's their duty t下列物质中，不含有硅酸盐的是 A．水玻璃       B．硅芯片         C．黏土              D．普通水泥