Question: Under which condition is a Debit/Reserve Units Request[Terminate] NOT sent to the Online Charging System (OCS) in an ABC Credit-Control session?
Option 1: When a TDF session is deactivated
Option 2: Upon successful recharge of the subscriber's account balance
Option 3: When Session termination is indicated by the OCS due to Credit Limit Reached
Option 4: Upon receipt of an Abort-Session-Request from the OCS
Explanation: The correct answer is Option 2, as successful recharge of the subscriber's account balance is not a trigger for sending a Debit/Reserve Units Request[Terminate] to the OCS. The other options are explicitly mentioned conditions under which this request is sent.