Aserious safety hazard created by engine exhaust is a. mild burns. b. sulfuric acid. c. carbon monoxide gas. d. electric resistance.

Which of the following statements is not true about regions? a.) regions have fixed boundaries that are determined by the region's inhabitants.b.) a region can be defined by physical characteristics, such as climate, landform, and vegetation.c.) regions can change over time.d.) a region can be defined by human characteristics, such as language, government, and economic activity.e.) the same location can be considered part of multiple regions.