a chemical landfill is where chemical waste is stored once it has been used
if it is secure it means that the waste cannot pollute the environment through water, air etc
By the time the bubbles rose to the surface of the ocean, the bubble model proposes that simple organic molecules had formed inside. The bubbles burst upon reaching the surface, releasing those molecules into the air.
C they have different functions i think its the most accurate (btw this is MY opinion)
