问题如下：
3. Based on Exhibit 1, the correlation between the debt ratio and the short interest ratio is closest to:
选项：
A.−0.3054.
B.0.0933.
C.0.3054.
解释：
A is correct.
The correlation coefficient equals the covariance between
variables X and Y divided by the product of the standard deviations of
variables X and Y, as follows:
老师，在线性回归方程里，自变量X和因变量Y的相关系数，不是等于cov(x,y)/x的方差吗？在计算样本时，成了cov(x,y)/（x的标准差✖y的标准差）了呢
