What would be the cause of A correctly-formatted entry has been added to /etc/hosts.allow to allow certain clients to connect to a service?

A correctly-formatted entry has been added to /etc/hosts.allow to allow certain clients to connect to a service, but this is having no effect. What would be the cause of this?

A.
tcpd needs to be sent the HUP signal.

B.
The service needs to be restarted.

C.
The machine needs to be restarted.

D.
There is a conflicting entry in /etc/hosts.deny .

E.
The service does not support tcpwrappers