Final answer:
The altimeter, airspeed indicator, and vertical speed indicator are the instruments that operate off the pitot/static system, with the correct answer being A. Altimeter and airspeed indicator.
Step-by-step explanation:
The instruments that operate off the pitot/static system are the altimeter and airspeed indicator, as well as the vertical speed indicator. Specifically, the correct answer to the question is:
A. Altimeter and airspeed indicator
The altimeter measures the aircraft's altitude by sensing changes in atmospheric pressure and converts these into altitude readouts. The airspeed indicator utilizes the pitot tube to measure dynamic pressure which, when combined with static pressure, determines the aircraft's speed relative to the surrounding air. Lastly, the vertical speed indicator, also connected to the static system, indicates how rapidly an aircraft is ascending or descending.