Let's assume that the functional relationship between the remaining fuel quantity y (liter) and the driving time t (hour) is: y=kt+b,
∴b=252k+b=9,
Solution: k =? 8b=9,
∴ The functional relationship between the remaining fuel quantity y (liter) and the driving time t (hour) is: y=-8t+9, so the option is correct;
② Refueling on the way is 30-9=2 1 (liter), so the option is correct;
③ The fuel consumption of the automobile is (25-9)÷2=8 liters/hour,
∴30÷8=3.75,
∴ The car can still run for 3.75 hours after refueling, so the option is wrong;
From a to b, the distance between the two places is 500 kilometers. Before and after refueling, the car runs at a constant speed of 100 km per hour.
∴ Need: 500÷ 100=5 (hours),
∴ When the car reaches the second place, there is still 30-8×(5-2)=6 liters in the fuel tank, and the option is correct;
So choose: C.