Which 2 statements about the safe distance from the vehicle ahead are correct? Select TWO

1. ①On a downhill road, braking distance becomes longer, so keep more distance than on flat ground.
2. ②A car with ABS (anti-lock braking system) has a much shorter braking distance, so the safe distance may be shortened.
3. ③If you drive at the same speed as the vehicle ahead, you will both skid the same distance if it brakes hard, so no gap is needed.
4. ④When you are tired or drowsy, it takes longer to notice danger and press the brake, so keep more distance.