An auditor is studying a ratio of accounts receivable growth rate to sales growth rate. Which of the following indicates a potential risk of collection problem in accounts receivable?

a. Sales grew by 10% and receivables grew by 11% from year one to year two.

b. Sales declined by 2% and receivables declined by 7% from year one to year two.

c. Sales grew by 10% and receivables declined by 2% from year one to year two.

d. Sales grew by 5% and receivables grew by 17% from year one to year two.