What is the consequence of a blocked static port?

A blocked static port can significantly disrupt the functioning of all instruments that rely on static air pressure for their readings, which is why the selection indicating that it can affect all pitot-static instruments is correct. The static pressure is used by several critical instruments, including the altimeter, vertical speed indicator, and the airspeed indicator.

When the static port becomes blocked, these instruments cannot accurately gauge the current atmospheric pressure, leading to erroneous altitude readings, potentially incorrect rate of climb or descent, and flawed airspeed data. This is particularly dangerous during flight, as pilots depend on these instruments for altitude awareness, climb or descent rates, and speed, all of which are necessary for safe operation and navigation.

The other options fail to capture the full scope of the problem. It’s not just the airspeed indicator that fails; the entire system of pitot-static instruments is compromised by the blockage. There's also not a negligible impact on instrument readings—aircraft safety depends on the accuracy of these instruments under all flight conditions. Finally, while rapid altitude changes may exacerbate sensing errors, a blockage of the static port is detrimental regardless of the altitude change rate.