Some Populations Like the Polynesians, the San, or the People

Some populations like the Polynesians, the San, or the people of northern India have phenotypes that do not fit neatly into "standard" racial categories, which suggests that

A) it is best to classify humans into a large number of racial categories.
B) phenotypical variation between human populations involves gradual shifts across different geographic zones.
C) these populations must have originated sometime before the major racial groups originated.
D) traditional concepts of race need to be reworked so that they are more exclusive.
E) there has been a lot of gene flow in the time since the origin of the three major human races.