proof check this with a reason and annotation

2. It is false that if we continue to use gasoline, then the air will not be polluted. Either we do not continue to use gasoline or we use solar power. If we continue to use gasoline and air-pollution control devices are perfected, then the air will not be polluted. Therefore, we use solar power if and only if air-pollution control devices are perfected. (G: We continue to use gasoline; A: The air will be polluted; S: We use solar power; P: Air-pollution control devices are perfected)