Which of the following is true about sources of stress? a. they vary based on age and location. b. they are stable across the lifespan. c. they have little impact on health. d. they are eliminated by therapy.

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.