Which of the following best explains why making automobiles completely safe is not efficient? a. Because human life is priceless, automobile safety generally doesn't matter. b. After some level of safety is reached, making cars even safer will not be worth the additional cost. c. The marginal benefit from additional automobile safety will generally rise as automobiles are made safer, more than offsetting the opportunity cost involved. d. Economic efficiency suggests that automobiles should be made as safe as humanly possible.