Do not answer it if you do not know 1. what are emissions? (0.5 points) 2. what two types of fuel do vehicles usually run on? (1.0 points) 3. list at least three alternative fuels or energy sources. (1.5 points) 4. what two types of energy source does a hybrid vehicle usually use? (1.0 points) 5. list at least two things people can do to conserve fuel. (1.0 points) 6. list at least three things people are doing to design transportation systems that are better for the environment. (1.5 points) 7. what is public transportation? (0.5 points) 8. list at least four types of public transportation. (2.0 points) 9. what is population density? (1.0 points)