题目

What happened in the telephone conversation? A . The phone line went dead. B . There was something wrong with Mr. White. C . The secretary stopped the conversation. 答案：A已知数列{an}是首项为1,公差为d(d≠0)的等差数列,a2,a5,a14依次成等比数列,则an=________;数列{an}的前n项和Sn=________.