A is the only right answer. The comet was discovered by Edmond Halley, so it is Halley's Comet. "Halley" rhymes with "alley" (though in his day he probably said it closer to "Haw-ley"), but some people tend to pronounce it so it rhymes with "daily." Regardless, it's not spelled that way, and the dude's name is not Haley or Hailey. (And obviously since it belongs to him the choices C and D are out of the question as they don't indicate the possessive.)