The kind of goods that are normally consumed together like peanut butter &jelly and bacon & eggs are called complementary goods. The correct answer is A.
The correct options are as follows:
1. Human skin color variation is primarily determined by the type and amount of melanin pigment in the skin.
2. Human skin color variation likely evolved in response to differences in the intensity of sunlight around the world.
3. Human skin color evolve recently in hominid evolution, once some population of human ancestor migrated out of Africa.
The color of human skin is primarily determine by melanin. The intensity of the sun in the climate where one is living also affect the type of skin color that will dominate in a geographical area.
B. the units are based on multiples of 10
this is true because when you convert it makes conversion a lot easier then if you are not using the metric system