Explanation
Every additional ask roughly halves the response to the first, which makes the standard follow, like and share ending three ways of asking for nothing. Choosing one is the entire skill, and the correct choice is usually the cheapest action that still serves the goal.
Cost to the viewer is the ordering principle: comment beats click, and click beats sign up, on response rate, every time. Comment requests are particularly undervalued because they also generate the engagement signal that lifts distribution.
The common mistake
Putting a CTA on a video designed to loop. The ending is where the loop closes, and interrupting it usually costs more distribution than the request earns.