Why would this happen?

LenoxSoft sends an operational email to all prospects, but finds there are some prospects that did not receive the email.

Why would this happen?
A . The prospects were set to “true” for opted out and set to “false” for do not email.
B . The prospects were on a suppression list used on theoperational list email send.
C . The prospects are opted out of the list used on the operational list email send.
D . The prospects were set to “false” for opted out and set to “true” for do not email.

Answer: D