题目

________from the Song Dynasty, the Confucian Temple of Nanjing has now developed into a famous scenic spot, ________sightseeing, shopping and tasty foods.   A. Having dated; featured           B. Dating; featuring C. Dating; having featured            D. Dated; featuring 答案：B18．已知a＞0，a≠1，等比数列{an}，a1=a，公比q=a，又数列{bn}的前n项和为Sn，Sn-Sn-1=lga${\;}_{n}^{{a}_{n}}$，（n≥2），b1=alga（Ⅰ）求Sn；（Ⅱ）要使数列{bn}中的每一项总不大于它后面的项，求a的取值范围．