The correct answer is: A. 1 and 2
Statement 1 is correct. Ozone is used as a germicide, air and water purifiers, in making artificial silk, etc.
Statement 2 is also correct. Bitterness in onions is due to the presence of sulphur compounds.
Statement 3 is incorrect. Helium is not used in filling the tyres of aircraft. Instead, nitrogen is used.
Nitrogen is used in aircraft tyres because it is less flammable than helium. Helium is also lighter than air, which could cause the aircraft to become unstable.