The fuel efficiency of passenger cars has increased significantly since the 1970s. A linear model of this situation is given below, where x represents the number of years after 1970, and y represents the average miles per gallon. Interpret the slope. A. For each year since 1970, passenger car fuel efficiency has increased by 0.29 gallons per mile.

B. For each year since 1970, passenger car fuel efficiency has increased by 13 gallons per mile.

C. For each year since 1970, passenger car fuel efficiency has increased by 0.29 miles per gallon.

D. For each year since 1970, passenger car fuel efficiency has increased by 13 miles per gallon.