Using Average (As Opposed to End-Of-Period) Values in Ratio Analysis

Using average (as opposed to end-of-period) values in ratio analysis is most appropriate when:

A) both values in the ratio come from the income statement.
B) both values in the ratio come from the balance sheet.
C) one value comes from the balance sheet and one value comes from the income statement.
D) Both a. and b. are correct.
E) All of the above are correct.