A decrease in quantity demanded: a. is illustrated by a movement upward and to the left along a demand curve.
b. increases the slope of the demand curve.
c. shifts the demand curve to the right.
d. is illustrated by a movement downward and to the right along a demand curve.
e. shifts the demand curve to the left.

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.