题目

阅读短文，从每题所给的四个选项 (A、B、C和D) 中，选出最佳选项。 Onthe day the tornado hit, there was no sign that the fierce weather was on itsway —the sky was blue and the sun had been out. The first warning my husband,Jimmy, 67, and I, 65, got came around 9 p.m., from some text on the TV Jimmywas watching. He ran upstairs to find me in our third-floor bedroom, and wechanged the channel from the national television to our local Pensacola,Florida, station. Soonthe tornado was on top of us. It was the loudest thing I had ever heard. Thehouse shook, and the power went已知递增的等差数列的前项和为，，，成等比数列，且的最小值为.（1）求；（2）设，求数列的前项和.