What is a Nagios service dependency?
a) A relationship between two Nagios services that requires one service to be functioning correctly in order for the other to function correctly
b) A relationship between a Nagios service and a host that requires the host to be functioning correctly in order for the service to function correctly
c) A relationship between two Nagios hosts that requires one host to be functioning correctly in order for the other to function correctly
d) A relationship between a Nagios object and a contact group that requires the contact group to be notified if the object has a problem