By 2009, american car manufacturers were required to meet minimum fuel efficiency standards that increased the average miles per gallon to 27.5. by 2016, that standard will increase to 39 mpg. what effect will this have? a. increased air pollution b. decreased fuel efficiency c. increased water pollution d. decreased energy consumption

The correct answer is D. decreased energy consumption. 
This measure is implemented for few reasons:
1. The fossil fuels are expendable, so they have to be managed carefully.
2. The economic power of the people will benefit.
3. Decreasing the pollution.
4. Dependence on fossil fuels, thus giving more time and space for developing alternative fuels, like the algae fuel for example...

So  if  the sum of the enthalpies of the reactants is greater than the products, the  reaction  will be  exothermic.  if  the products side has a larger enthalpy, the  reaction  is  endothermic. you may wonder why  endothermic reactions, which soak up energy or enthalpy from the environment, even happen

Answera discharge of static electricity;