Which of the following is a test of controls?

1. Examine a sample of sales invoices to determine whether prices agree to the approved price list

2. Confirm accounts payable directly with vendors

3. Examine a sample of warehouse removal slips for signature of authorized officials

4. Foot the accounts payable trial balance and compare the total with the general ledger

a Items 1, 3, and 4

b No choices are tests of controls

c All choices are tests of controls

d Item 3 only

e Items 1 and 3