Which is true of mandatory monthly proficiency demonstrations?

A$.$ Live messages sent to IPAWS will be counted as a monthly proficiency demonstration.

B$.$ IPAWS users are required to send a successful demonstration message at least once a month to the IPAWS Test$/$Demo Environment.

C$.$ Alerting Authorities can fail to demonstrate their proficiency in the IPAWS Test$/$Demo Environment and continue to send alerts through IPAWS.

D$.$ It is optional for all IPAWS users.