Which of the following statements is true? a. matter and energy do not interact. b. energy can change from one form to another. c. energy does not transfer from place to place. d. energy cannot be stored.

Automobile fuel efficiency is often measured in miles that the car can be driven per gallon of fuel (mpg). heavier cars tend to have lower fuel efficiencies (lower mpg ratings). which variable (weight or fuel efficiency) is most naturally considered the explanatory (predictor) variable in this context?