Which number on the timeline represents the period in which the american civil war was fought? a) 1 b) 2 c) 3 d) 4

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.