题目

--- -When did he get his first novel published? ---- It was in 2008 ____  he was still in high school. A. that           B. since          C. when         D. which 答案：C 解析: 略已知数列{an}的通项公式an=22n-1，Sn表示{an}的前n项和，则S4等于（ ）A．682B．170C．85D．42