Blockage of the static source of atmospheric pressure (Static ports) leads to the failure of which of the following instruments?

Static ports provide ambient atmospheric pressure reference for the pitot-static system. The alteter uses this to indicate altitude above a reference level. The ASI uses both pitot pressure (total pressure) and static pressure to calculate airspeed. The VSI uses the rate of static pressure change to indicate climb or descent rate. Therefore, blocked static ports cause all three instruments to fail or give erroneous readings.