题目内容：
根据下列材料，请回答题There are stock markets(股票市场) in large cities in many countries. The stock exchange is a place where people can buy or sell shares of a factory or company. And each share means certain ownership of a factory or company.
Different people go to stock markets. Some are rich, who want to get more money than they have. Others are not very rich, who buy stocks to try to become rich. Still others buy stocks as part of their plan to save money.
Of course, investing(投资)money in the stock market is not the safest way to make money.No one can tell exactly whether the shares will be doing well. The factory or company may do badly. Then the stocks will go down, and the investors will lose money. The stock may go up or down for a number of untold reasons. Everyone wants the stock to go up, but sometimes even if a factory or company does a good job, the stock may still go down.
No wonder going to the stock market is often compared to gambling(Ill,t). Factories and companies that need money are pleased that so many people are willing to "gamble". Indeed, the stock market is an attractive and complex part of the business world.
If you are a good investor, _________in the stock market. A．you can always make money
B．you cab tell exactly when the stock goes up or down
C．you may sometimes lose money-
D．your gambling is always safe
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