Answer: option A. 9.2 gal/year
Justification:
The average rate of change from 1960 to 1970 is the change on the variable gallons consumed per passenger car divided by the period
average rate of change = Δg / Δt
Δg = 760 gallons - 668 gallons
Δt = 1970 year - 1960 year
760 gal - 668 gal 92 gal
average rate of change = -------------------------------- = ---------- = 9.2 gal / year
1970 year - 1960 year 10 year
Answer: 9.2 gal / year
As you see for this specific period, 1960 to 1970, the vehicles increased their consumption of gas per passenge, meaning that they became less efficient.