You can prevent students from responding to announcements by enable the option in the course settings. This option will disable comments for all future announcement postings (older announcements will still allow responses unless you manually disable that option). You will only need to do this once per course.
- Click Settings in the course toolbar.
- Scroll down and click more options.
- Find where it says “Disable comments on Announcements” and select that checkbox.
- Click Update Course Details at the bottom of the page.
For screenshots and additional information, please see How do I disable comments on announcements in a course?
A single announcement
If you want to prevent students from replying to an announcement that has already been posted:
- Go to the announcement.
- Click the three dots to the right of the announcement.
- Choose “Disallow Comments”.
For screenshots and additional information, please see How do I close an announcement for comments in a course?