What type of pollution did mexico city face a. water b. soil c. air

What role did natural resources play in african politics?

Which choice best describes the general trend for the countries shown, for the period 2008 - 2010?

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.