I need more explanation on both E and F option. Why they are correct or wrong.

3. Which of the following uses of computer-assisted audit techniques would assist the auditor in a test of thecompleteness of revenue?

E.Selecting 50 items from the accounts receivables population by reference to a random number function in the audit software. The 50 items are then vouched to sales invoices.

F.A sequence check looking for missing sales invoice numbers.