Exam MS-203 topic 4 question 95 discussion

B is correct

should be B, you need SPF for that

To ensure that email messages sent from the unauthorized IP addresses of any sending domain are marked as High confidence spam in a Microsoft 365 subscription that uses Microsoft Exchange Online Protection (EOP) with the default settings, you should create a mail flow rule1. The other options, setting SPF record: hard fail to On or Conditional Sender ID filtering: hard fail to On for the default anti-spam inbound policy or adding an entry to the IP Block List for the default connection filter policy, are not mentioned as options for ensuring that email messages sent from unauthorized IP addresses are marked as High confidence spam.