A. key signature , the key signature is a list of all the sharps and flats in the key that the music is in.
The Music Industry is containing and composing of not only companies but also individuals that making money by writing new pieces of songs, selling live shows and concerts, audio and video recordings and compositions of sheet music. These people called songwriters and composers, musicians, recorders, bandleaders, publishers, and producers, and etc.
But the companies that will be going to create, produce and distribute its musical scores are the Music Publishing companies.
It's important because in a person's life, there will be things that are risky (hard).
There will be options in your life that you will need to make. There also things you may need to be aware of, so not every time you may be lucky.