The first step for any test of the occurrence $($existence$)$ assertion for payroll expense is

a$.$ Assuring that the total gross pay on the payroll register agrees with the amount of the expense line item on the income statement

b$.$ Footing the payroll register used to select a sample

c$.$ Selecting a sample of supporting documentation to trace to the payroll register

d$.$ Selecting a sample of payroll expenses to vouch to supporting documentation