Definition: In this task, you are given a multiple-choice question about healthcare. Answer the question based on your information and classify your answers into '1', '2', '3', and '4'.
Input: Question: Mitochondrial oxidative phosphorylation is regulated by: 
 Options:  <1> Mitochondrial steroid hormones. <2> Apoptosis <3> Thermogenin <4> The cytochrome c. <5> The cellular energy charge.
