Final answer:
The PIC shall comply without question with ATC instructions and clearances. They can request clarification if needed.
Step-by-step explanation:
When dealing with ATC instructions and clearances, the PIC (Pilot in Command) shall comply without question. The PIC is responsible for the safety of the flight and should follow the instructions given by Air Traffic Control (ATC) without hesitation. It is important to note that the PIC can always request clarification if needed, but challenging ATC instructions should only be done if there is a genuine doubt about the safety of the aircraft.