Primary or main medium of Performance Art

Review the following short videos and respond to the corresponding questions.
Performance Art: https://www.youtube.com/watch?v=EmMTKdUAokM

1. What is the primary or main medium of Performance Art?
2. What was artist Joseph Beuys' famous statement about art?
3. What is the designed intent or purpose of Performance Art?
4. In your opinion, is Performance Art a valid art form? Why or why not?