Treat the passenger as if she/he is your boss...
...because she/he is...
1) Passengers that ask about engine run-ups in the Beech 1900 might remember prior flights where the crew completed First Flight of Day checks with pax onboard.
2) Pax that ask about sleep, drinking, experience, etc have read NTSB reports that have listed those issues as contributing factors in accidents.
3) PAX that ask technical questions deserve your best answer (it may be "I don't know") The Airbus a320 barking dog is hydraulics, but not just "pumps". It is the PTU - a 2 way reversible motor pump that uses the hydraulic energy of one system (green or yellow) to pressurize the second system without transferring fluid.
...they have a right to know...