In October 1987 the United States stock market suffered a major drop in prices. During the weeks after the drop, the volume of stocks traded also dropped sharply to well below what had been the weekly average for the preceding year.
However, the volume for the entire year was not appreciably different from the preceding year’s volume.
Which of the following, if true, resolves the apparent contradiction presented in the passage above ？（）
A．Foreign investors usually buy United States stocks only when prices are low.
B．The number of stock buyers in 1987 remained about the same as it had been the preceding year.
C．For some portion of 1987, the volume of stocks traded was higher than the average for that year.
D．The greater the volume of stocks traded in a given year, the lower the average price per share on the United States stock market for that year.
E．The volume of stocks traded rises and falls in predictable cycles.
参考答案：C
解析：
根据整体的一部分变小，而包含这部分的整体大小未变，我们很容易推出这个整体中的另一部分一定变大，以此来补偿变小的这一部分，因此1987年股票的交易量未变一定是由于1987年某一段时间股票的交易量较高补偿了交易量较低的那几周减少的交易量。由此分析可知(C)为正确答案。