Viola Co – Study Hub practice question

As part of your overall review, you have performed analytical procedures over the draft financial statements and have noted that the trade receivables collection period is lower than it was during the interim audit performed in October 20X4. You are aware that the credit controller of Viola Co left the company in November 20X4 and that the directors have said that, as a result, the company is experiencing difficulties in debt collection.

Which of the following is a valid explanation for the INCONSISTENCY between the results of the analytical procedures on trade receivables and the directors’ statement regarding debt collection problems?
A.A change in sales mix towards high value products
B.An increase in the proportion of cash sales since November 20X4
C.An increase in the rate of sales tax in December 20X4
D.Sales growth of 1% per month over the year

The correct answer is B, however, I thought revenue figure used in calculating receivables days include credit sales only and not cash sales and so, the increase in cash sales should not affect the calculation.
Could you please clarify this?

Thank you in advance,
Iniss.