Bronze consist of a mixture of copper and ?

Whether or not a given study has the possibility of causing harm to participants:

The president’s role in a political party is to set the legislative agenda true or false

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.