题目

Last week, I read a world-famous book ________ Around the World in Eighty Days.    A. called                  B. calls                         C. is called                    D. is calling 答案：A设各项均为实数的等比数列{an}的前n项和为Sn，若S10=10，S30=70，则S40等于（ ）A．150B．-200C．150或-200D．400或-50