The Knight Bus is summoned by sticking out your wand arm, as Harry does when he runs away from the Dursleys in Book 3 (Prisoner of Azkaban). The bus appears for stranded wizards in need. Option C is correct. Options A and B are incorrect because there's no specific charm or bus stop involved. Option D is wrong because wizards CAN summon it using the proper method. The bus driver and conductor (Stan Shunpike) then collect passengers.