Graphing only works in radian mode and is convenient for mathematics. Degrees are what most people understand. Gradians are used mainly in surveying and are convenient when working with vectors in the complex plane. Turns are used mostly for the windings of electromagnets and angular speed of rotating machinery (RPM). (360 degrees = 2pi ... 400 gradians = 2pi ... 1 turn = 2pi)
Oh god... I once had it on radians for the entirety of the quiz, and realized it was so 10 minutes before class ended and it was just a mess... I ended up failing that quiz lol
I liked that movie.