Please choose the correct answer to the 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?

Answer1: gasoline evaporating from soil Answer2: gasoline catching fire in the soil Answer3: gasoline polluting an old septic system Answer4: gasoline trickling down into groundwater

Answer format: answer1/answer2/answer3/answer4