Use this fact to answer the question: microorganisms cause food to spoil

A team has pizza after a game, and they eat most of it, but leave the rest of the pizza out. The pizza is later inedible because of

Pick your answer from: [i] need to play games; [ii] bedtime coming sooner than thought; [iii] lack of food preservation; [iv] exhaustion from the sun;

The answer is:
[iii]