Identifying which instruments use the static port is essential. Which of the following instruments uses the static port?

The static port is essential for measuring atmospheric pressure, which directly informs certain flight instruments. Among the instruments connected to the static port, the altimeter relies on the pressure difference to determine altitude by measuring changes in the ambient air pressure as the aircraft ascends or descends. The airspeed indicator also uses the static pressure to calculate true airspeed by comparing the static pressure to the dynamic pressure from the pitot tube, which measures the pressure due to the aircraft's speed.

Thus, both the airspeed indicator and altimeter utilize the static port to function correctly, making the choice that includes both of these instruments the most accurate answer. The other options single out only one instrument or include instruments that do not rely on static pressure, which is why they are not the correct choice in this scenario.