How do you prevent users from posting transactions into a prior accounting period?

How do you prevent users from posting transactions into a prior accounting period?

A.
Populate the Allow Posting To field on the General Ledger Setup window.

B.
Check the Date Locked field in the relevant accounting period record.

C.
Check the Closed field in the relevant accounting period record.

D.
Populate the Allow Posting From field on the General Ledger Setup window.