E4E11 - Amateur Extra Class

E4E11 : What could be the cause of local AM broadcast band signals combining to generate spurious signals on the MF or HF bands?
A One or more of the broadcast stations is transmitting an over-modulated signal
B Nearby corroded metal connections are mixing and reradiating the broadcast signals
C You are receiving skywave signals from a distant station
D Your station receiver IF amplifier stage is overloaded
Correct Answer: Nearby corroded metal connections are mixing and reradiating the broadcast signals