Explanation:
The three activities that can increase or decrease a score in the baseline scoring system are unsubscribed from email, webinar attended, and form submission. A score is a numerical value that indicates the level of interest or engagement of a prospect in your products or services. You can use scoring rules to assign positive or negative points to prospects based on their activities, such as opening an email, clicking a link, or filling out a form. You can also use scoring categories to assign points based on specific products, services, or business units. The baseline scoring system is the default set of scoring rules that Marketing Cloud Account Engagement provides, and you can customize it to suit your needs. The baseline scoring system assigns points to the following activities:

Unsubscribed from email: -100 points. This indicates that the prospect is not interested in receiving your emails, and reduces their score significantly.
Webinar attended: +50 points. This indicates that the prospect is interested in learning more about your products or services, and increases their score considerably.
Form submission: +50 points. This indicates that the prospect is willing to share their information with you, and increases their score considerably.

Other activities that can affect the score in the baseline scoring system are:

Landing page error: -10 points. This indicates that the prospect encountered a problem with your landing page, and reduces their score slightly.
Assigned to a user: +15 points. This indicates that the prospect is ready to be contacted by a salesperson, and increases their score moderately.
Email open: +1 point. This indicates that the prospect opened your email, and increases their score slightly.
Email click: +3 points. This indicates that the prospect clicked on a link in your email, and increases their score slightly.
Email hard bounce: -10 points. This indicates that your email could not be delivered to the prospect, and reduces their score slightly.
Email soft bounce: -5 points. This indicates that your email was temporarily rejected by the prospect’s email server, and reduces their score slightly.