题目

已知数列是等比数列，为其前n项和，若，a4＋a5＋a6＝6，则S12等于( ). A．45    B．60     C．35      D．50 答案：A_____ abstract, Calileo's theory was quite difficult to understand of his time. [     ]A. Sounding B. SoundedC. To soundD. Having been sounded