Alex Trebek, who hosted “Jeopardy!” for a record-setting 36 years and brought an authoritative and unflappable persona to the quiz show’s peculiar conceit, in which questions are delivered as answers, died on Sunday. He was 80. The death was confirmed by the show’s producers. They said that episodes of the show hosted by Mr. Trebek would air through Dec. 25 and that they had not made plans for a replacement
