① According to the meaning of the question, the image passes through (0,25) (2,9),

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.