Answer from cs61c-cg (Daniel Lau 16776873) for Question 2
This is becasue the scheme implemented is more convinient, we can easily know that which slot in the cache the particular data should go to simply by moduling the address by the number of slot available for the cache.

If the high order bits is used to determine the cache location, we are not able to determine the acahe location with the mod. method