The concept of race is best defined as: __________
a. differences based upon ethnic variation between different nations or culture groups.
b. differences based upon linguistic variations such as the Indo-European language family versus Asiatic languages such as Mandarin or African Bantu languages.
c. differences based upon human-environmental factors such as how climates and resource availability can effect the prosperity of a region's population.
d. differences based upon the continent of a person's residence or origin.
e. differences based upon human physiological variations such as skin color and bone structure.