Answer:
The method that could be used to fairly choose the class president in the given scenario is flipping a fair coin. This is because flipping a fair coin is a random process and both candidates have an equal chance of winning. This ensures fairness in the selection process. Asking a group of senior teachers or letting the two candidates mutually decide who should win may introduce biases and may not be fair to both candidates. Rolling a biased die may also introduce unfairness as the outcome is not random and is predetermined.