In a pair programming scenario, the roles of driver and navigator can be assigned in various ways, depending on the team's preferences and dynamics. However, one common approach is to have each programmer switch roles frequently, allowing both to experience the responsibilities of both the driver and navigator. Therefore, the most fitting response from the options provided would be:
Each programmer is either the driver or the navigator randomly at the start of each session and switch roles frequently.
This method promotes collaboration and allows both members to learn from each other, rather than strictly assigning roles based on experience or seniority.