Which feature, when set to zero, might allow a GPS unit to have an accuracy equivalent to Precise Positioning Service receiver capability?

Correct Answer: Option D — Selective Availability

Selective Availability (SA) was an intentional degradation of the GPS signal introduced by the Department of Defense to limit civilian accuracy. When SA was set to zero or turned off, civilian GPS receivers achieved significantly higher precision, approaching the performance levels previously reserved for the military's Precise Positioning Service.