gasoline evaporating from soil gasoline catching fire in the soil gasoline polluting an old septic system gasoline trickling down into groundwater
I am hesitating between 4 options to answer the following question, which option should I choose?
Question: A student wants to create a model showing the most important reason why old gasoline should never be poured into the soil. Which of the following must be included in the model?
Possibilities:
- gasoline evaporating from soil
- gasoline catching fire in the soil
- gasoline polluting an old septic system
- gasoline trickling down into groundwater

gasoline trickling down into groundwater