An auditor suspects that fictitious sales may have been recorded during the year. Which of the following analytical review results would most likely indicate that fictitious sales were recorded? 

a. Uncollectible account write-offs increased by 10 percent, sales increased by 10 percent, and accounts receivable increased by 10 percent. 

b. Gross margin decreased from 40 to 35 percent.

c. The number of day's sales in accounts receivable decreased from 64 to 38. 

d. Accounts receivable turnover decreased from 7.1 to 1 to 4.3 to 1.