The correct answer is A. the severity level of email notifications.

To ensure that the security administrator receives email alerts for all the activities, you need to configure the severity level of email notifications in the Security Center settings. By default, email notifications are only sent for alerts with high severity. You can change this setting to include alerts with medium or low severity as well. This way, you can receive email alerts for activities such as antimalware action failed and suspicious network activity, which have medium or low severity