The correct answer is B: Blocking access by other users. Using excessive effective radiated power (ERP) on a satellite uplink causes blocking access by other users. When you use too much power, your signal can overload the satellite's receiver or create interference that prevents other operators from using the satellite. Satellites are shared resources, and excessive power is antisocial and violates good amateur practice. For amateur radio operators, using only the minimum power needed (typically 5-10 watts for most satellites) ensures fair access for all users and prevents satellite overload.