What is the advantage of defining the Service field in a rule for a specific server?

What is the advantage of defining the Service field in a rule for a specific server?

A.
it allows you to permit and deny specific services.

B.
It allows you to drop traffic that does not match the service.

C.
There is no advantage to defining the Service field in any rule.

D.
It makes the rule more efficient, allowing IDP to only match attacks against services that would
actually affect that server.