问题
单项选择题
For a stock, which of the following is NOT a random variable（）
A. Its most recent closing price.
B. Its P/E ratio.
C. Its stock symbol.
答案
参考答案：C
解析：
A random variable must be a number. Sometimes there is an obvious method for assigning a number, such as when the random variable is a number itself, like a P/E ratio. A stock symbol of a randomly selected stock could have a number assigned to it like the number of letters in the symbol. The symbol itself cannot be a random variable.