What is a runway incursion and what ramp safety practices minimize its risk?

What is a runway incursion and what ramp safety practices minimize its risk?

• A. Weather phenomenon; rely on windsocks.
• B. Normal taxiing; ignore radios.
• C. Only occurs during takeoff; no procedures.
• D. Unauthorized aircraft or vehicle on a runway; minimize risk with clear clearance procedures, good radio discipline, and trained spotters.

Answer: (D)