问题：

[单选] What is the purpose of an explicit "deny any" statement at the end of an ACL？（）

A . none，since it is implicit
B . to enable Cisco IOS IPS to work properly；however，it is the deny all traffic entry that is actually required
C . to enable Cisco IOS Firewall to work properly；however，it is the deny all traffic entry that is actually required
D . to allow the log option to be used to log any matches
E . to prevent sync flood attacks
F . to prevent half-opened TCP connectio