I dont know the answers please help

Which choice best describes how your answer compares to the sample

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.

The second westward surge reached the: mississippi river, appalachian mountains, oregon territory