The APU (Auxiliary Power Unit) is typically used to:

Supply electrical power and bleed air on the ground (and in some cases in flight)

Correct

Provide emergency thrust

Drive the hydraulic pumps only

Cool the avionics bay

Explanation

The APU provides electrical power and pneumatic (bleed) air, primarily for ground operations and engine starting.

Test yourself with random questions from Aircraft General Knowledge and all other ATPL subjects.