Which of the following is best practice to put at the end of an ACL?

An implicit deny at the end of an ACL acts as a catch-all that blocks all traffic not matched by a preceding permit rule, enforcing the principle of least privilege. Without this, some platforms may default to allowing unmatched traffic, creating unintended security gaps where unauthorized traffic passes through.

Time-of-day restrictions are conditional modifiers applied to individual ACL permit or deny entries and are not a standard final rule providing default-deny security coverage.

An implicit allow at the end of an ACL would permit all traffic not matched by earlier rules, which is the opposite of security best practice and creates significant exposure.

An SNMP community string is used for network device management authentication and is not a valid entry type within an access control list.