Please choose the correct answer to the question: A student concludes that a chemical reaction performed in a classroom investigation was exothermic. To communicate the validity of this conclusion, which would make the best visual evidence in a presentation?

Answer1: photographs of reactants and products Answer2: listing of masses of reactants and products Answer3: listing of time from start to finish of reaction Answer4: photograph of a flame produced when the chemicals reacted

Answer format: answer1/answer2/answer3/answer4