In studying expressions of basic emotions, Ekman compared people in the US and in New Guinea because:

A. They had no technology so they were assumed to be less intelligent (thus, their emotions must be basic).
B. The tribesmen were cheaper to study than Americans who ask for a lot of compensation for their time.
C. The tribesmen had never seen anyone from outside their area so they could not have copied their expressions.
D. None of the above.