Can someone pls help me

What would you call a political system that is only meant to last for a short time

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.

1u.s. history question! question: how did world war ii change the united states' position in world affairs? i need good explanation to support the answer otherwise i get docked points. real answers only ! you! : )