What is the default value for the Drop Ad Hoc Conference service parameter?

What is the default value for the Drop Ad Hoc Conference service parameter? (Source:Preventing Toll Fraud)

A.
Never

B.
When No On-Net Parties Remain in the Conference

C.
When No Off-Net Parties Remain in the Conference

D.
Drop Ad Hoc Conference When Creator Leaves

Explanation:
Incorrect answer: BCD
To use the additional functionality that advanced ad hoc conferencing provides, Cisco

recommends that you set this service parameter to Never. Any other setting can result in unintentional termination of a conference.
Link:https://www.cisco.com/en/US/docs/voice_ip_comm/cucm/admin/8_6_1/ccmsys/a05confb.html