What is one of the most valuable parts of music theory and why?

To memorize all major and minor key signatures and practice spelling chords until it just becomes second nature to you, take to heart the things you learn.
Because if you know these basic things you will soon be able to compose or put together your own music~ sorry if this sounded cheesy

Goodest should be best

Answer (b) create a social media account and share clips of their recordings;