听力原文： A New York stock exchange stops trading after the steepest falls in share prices

for ten years. Following earlier falls in Hong Kong, stocks fell steadily from the opening of trading on Wall Street. Amid hectic scenes on the market floor, trading was suspended twice. When the second suspension was triggered, business was halted for the day. By then, the Dow Jones index has fallen by 554 points, the steepest fall since the market crash of 1987. The United' States Treasury tried to calm the market, stressing the strength of the American economy. Throughout the day, the Treasury has been in touch with officials of the Federal Reserve, the Securities Exchange Commission and other members of the working group on financial markets. Measures to halt trading temporarily on days like today went into effect automatically as designed. Now, signs indicate that the payment and settlement systems and other market mechanisms are working effectively. Today and over the past several days, the Treasury has also been in touch with financial officials around the world and will continue to monitor development here and abroad on an ongoing basis. The fundamentals of the United States economy are strong and have been for the past several years and the prospects for continued growth with low inflation and low unemployment are strong.

A New York stock exchange stops business because ______.

A．share prices reach a record low.

B．trading has been suspended twice.

C．the world economy is rather weak.

D．market mechanisms are not functioning well.