For each scale presented, decide whether it is Major, Pure/Natural Minor, Harmonic Minor, or
Melodic Minor (ascending only). Checking the step between scale degrees 7 and 8 is a fast way to
begin narrowing things down, pure minor is the only scale with a whole step between scale degrees 7 and 8.
Another good place to check is between scale degrees 2 and 3,
Major is the only scale with a whole step there. The difference between a melodic minor and harmonic minor scale is between
scale degrees 6 and 7. Knowing your circle of fifths is also very helpful here.