Is it fair to assume that if AC C wasn't available AC B would be the best option, because its asking which one MOST helps justify?

For #3 if you negated "classes" in the original statement so 3+→/C, would it be correct for the negation to be 3+ and C (We can have 3 inches of snow and class) or is this not correct logically?

In an LSAT book I read it states that "some" means 1%-50% of whatever we're taking about because once its over 50% then it becomes "most" it can not mean "some" anymore. But here J.Y says that "some" can mean 1%-100%. So what should I believe more when the LSAT says "most" vs "some" or is there really no difference as long as I know most means 51%-100% or am I just overcomplicating things?