单选题 Passage One
The term profit in economics has a very precise meaning. Economists, however, often loosely refer to "good deals" or profitable ventures with no risk as profit opportunities. The general view of economics is that profit opportunities are rare. At any one time there are many people searching for such opportunities, and as a consequence few exist.
At major banks in big cities, you can buy foreign currencies. The prices of these currencies are determined in world markets. With dollars we can buy marks, with these marks we can buy francs, and with these francs we can buy back dollars. If, for example, the dollar-franc price is too low with respect to the other prices, there is an immediate rush to buy dollars and sell francs, not by ordinary citizens at bank windows, but by a few large currency traders in Tokyo or New York who watch prices every minute. Such a rush drives up the dollar-franc price to the no-profit-opportunity point. There are in fact almost never any profit opportunities of this kind in foreign currency markets. Markets like this, where any profit opportunities are eliminated almost immediately, are said to be efficient markets.
The common language way of expressing the efficient markets hypothesis is "there's no such thing as a free lunch." How should one react when a stock broker calls up with a hot tip on the stock market? With doubt. There are thousands of individuals each day looking for hot tips in the market, and if a particular tip about a stock is valid, there will be an immediate rush to buy the stock, which will quickly drive its price up. By the time the tip gets to your broker and then to you, the profit opportunity that arose from the tip (assuming that there was one) is likely to have been eliminated.
This economists' view that there are very limited profit opportunities around can, of course, be carried too far. There are clearly times when profit opportunities exist. Someone has to be the first to get the news, and some people have quicker insights than others. Nevertheless, news does get spread quickly, and there are thousands of people with quick insights. The general view that profit opportunities are rare is close to the mark_

单选题 What do profit opportunities mean in economics?
A. Profitable businesses without any risk.
B. Business deals that produce profit.
C. Business opportunities that many people search for.
D. Trading foreign currencies and stocks.

单选题 What do economists think of profit opportunities?
A. Profit opportunities don't exist in economics.
B. There are few profit opportunities in economics.
C. Profit opportunities can improve efficiency in markets.
D. Only people with insights get profit opportunities.

单选题 Why does the author mention buying foreign currencies?
A. Because it illustrates the unity of world markets.
B. Because many ordinary citizens are interested in it.
C. Because it shows how profit opportunities disappear.
D. Because it is a business which may bring profit.

单选题 What do we learn about an efficient market from the passage?
A. Anyone who gets hot tips can gain profit.
B. People should choose a market not known by many.
C. Only experts can grasp profit opportunities.
D. Profit opportunities only last a very short time.

单选题 What is the author's attitude towards economists' view about "profit opportunities"?
A. Ironic. B. Doubtful.
C. Cautious. D. Positive.