You could look at the event monitoring subscription for this. Also See https://docs.moodle.org/33/en/Event_monitoring
There is an event called "Choice answer added" in the events list /report/eventlist/index.php
You would initially need to create an event monitoring rule for this event.
Then anyone subscribed to that event can get a notification every time a choice has been made.
Teachers, non-editing teachers and managers by default will be able to access event monitoring in their Preferences page.
For students to be able to subscribe, you would first need to override their permissions for "Subscribe to event monitor rules
tool/monitor:subscribe" in that particular course.
The user then needs to subscribe to the event themselves to receive emails. They can select to get notifications for a specific choice only, or for all choice activities on the course.