human
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?

Choices:
A) photographs of reactants and products
B) listing of masses of reactants and products
C) listing of time from start to finish of reaction
D) photograph of a flame produced when the chemicals reacted
gpt
The correct answer is 3: photograph of a flame produced when the chemicals reacted.