Final answer:
The b)Unit commander is responsible for determining which tasks in the STS apply to their unit's mission when developing a master task listing (MTL).
Step-by-step explanation:
When developing a master task listing (MTL), the individual responsible for determining which tasks in the specialty training standard (STS) apply to their specific mission is the b) Unit commander.
The Unit commander has the authority to tailor training to the unit's mission, resources, and personnel to ensure the effectiveness and efficiency of the mission.
The MTL is a comprehensive list that typically reflects the tasks that Airmen are expected to perform in their respective roles, and it is aligned with the mission requirements as assessed by command leadership.