题目

---Why not come and join us in the game, Linda? --- __________, but I have something to discuss with Mr Smith at his office now. A. Let's go    B. I'd like to         C. Yes, please        D. It's a pleasure 答案：B设集合W是满足下列两个条件的无穷数列{an}的集合：①②an≤M，其中n∈N*，M是与n无关的常数（1）若{an}是等差数列，Sn是其前n项的和，a3=4，S3=18，试探究{Sn}与集合W之间的关系；（2）设数列{bn}的通项为bn=5n-2n，且{bn}∈W，M的最小值为m，求m的值；（3）在（2）的条件下，设，求证：数列{Cn}中任意不同的三项都不能成为等比数列．