What the wheels are turning focus is required on task. Questions should aid practise rather than impede development.
As such questions should be limited to:
Closed Questions, around the goal of the session, providing they will help the client achieve the goal and the situation is appropriate.
Leading and Embedded Command Questions to manage risk, giving your pupil enough time to make decisions and be in control, accelerating their learning and keeping the instructor in control of the safety of the vehicle.
Open Questions to manage risk. It might be necessary to check the thoughts or feelings of the learner, on the approach to a junction, for example, to help manage risk and determine the level of support provided. These should be well-timed, short questions that can be answered simply. How are you feeling about this junction? (okay, great, nervous etc)
Open questions, in general, should be restricted to the side of the road, since they require too much focus and attention, as the purpose of an open question is to allow the pupil to explore their thoughts, beliefs, attitudes and emotions in depth.
The DVSA ADI 1 encourages us to:
Remember it is an offence to use a mobile phone whilst driving because this is known to create a level of risk equivalent to or, in some cases, greater than driving whilst drunk. It cannot, therefore, be good practice to constantly bombard the pupil with unnecessary questions.