The correct answer is A) Afrasiyab has him killed because he is suspicious of him.
Saiawush died when Afrasiyab has him killed because he is suspicious of him. Indeed Afrasiyab ordered to take Saiawush to a desert location and there he was beheaded. Some people tried to make Afrasiyab change his man, but there was no reason that could convince him to change his decision.
Saiawush was an Iranian prince of the great Empire of Iran. It is an important character in the story "The Epic of Kings," written by Ferdowsi in 1010 ACE.