In Calculating Each of the Last Six Months' Uncollected Balance

In calculating each of the last six months' uncollected balance percentages,the current accounts receivable balance is split into uncollected balances by month in which they originate.Then,each month's uncollected balance is divided by the __________________________________________.

A) current accounts receivable balance
B) sum of the accounts receivable balances from the last six months
C) credit sales for that month
D) the sum of the credit sales from the last six months