I’ve come to the conclusion that the hardest question from a supervisor to answer is:

How do you know that you are most effectively achieving progress towards your goal?

This is really hard to answer because, in order to answer it:

• you have to know what your goal is,
• you have to demonstrate progress towards the goal, which means that historical progress has to have been tracked,
• you have to show that you have looked at all alternatives to achieving the goal, and that no other process will have caused you have made more progress than you have made.