Why did slavery continue after the revolution?

The idea that desirable traits can be bred into human beings and undesirable ones can be bred out is known as:

Which example define natural rights ?

Which statement is a good description of a model? a) models are a description of nature based only on one or two variables. b) models are testable ideas but they are not very to most people. c) models are a description of nature that predicts more accurately than real events. d) models are an approximiation of a real system that omits all but most essential variables in a system.