Respuesta :
I think the correct answer among the choices listed above is option C. If there is too little air, natural gas won't explode because there is not enough oxygen. Ignition of the natural gas cannot happen because there is less oxygen present for an explosion to happen.
I would say C. Not enough Oxygen. Fires need oxygen to burn effectively also the same concept with rocket engine or normal vehicle engines, oxygen is used to make the minor fuel explosion in the engine which makes it an internal-cumbustion or an internal-explosion engine.