Which of the Following Is NOT a Reason That After-Date

Which of the following is NOT a reason that after-date receipts may be preferred as a test of accounts receivable in preference to obtaining external confirmations?

A) Replies from credit customers may not be reliable.
B) Credit customers may choose not to reply.
C) Letters would not be sent to customers who had incorrectly been excluded from the accounts receivable records.
D) External evidence is deemed less trustworthy than internal evidence.