Which three instruments are connected to the pitot-static system?

The correct selection includes instruments that are directly linked to the pitot-static system, which is crucial for measuring altitude and airspeed in aircraft.

The altimeter utilizes static pressure from the atmosphere to determine the aircraft's altitude above sea level. The Vertical Speed Indicator (VSI) also relies on static pressure differences to gauge the rate of climb or descent. The Airspeed Indicator (ASI) incorporates both static pressure and dynamic pressure created by the aircraft's forward motion; this allows it to present the speed of the aircraft relative to the surrounding air.

Together, these three instruments—altimeter, VSI, and ASI—are vital for pilots to maintain situational awareness regarding altitude and airspeed, both of which are fundamental for safe flying. The other options mention instruments like the Heading Indicator, which does not derive data from the pitot-static system, but rather from magnetic or gyroscopic sources, resulting in their exclusion from the correct answer.