选择题：满足a1=1，log2an+1=log2an+1(n∈N*)，它的前n项和为Sn

题型：选择题

I used to believe in the American dream that meant a job，credit and success. I wanted it and worked toward it like everyone else, all of us separately chasing the same thing.

One year, through a series of unhappy events, it all fell apart. I found myself homeless and alone. I had my truck and $ 56. I searched the countryside for some place I could rent for the cheapest possible amount. I came upon a deserted cottage in a small remote valley.I hadn't been alone for 25 years. I was scared, but I hoped the hard work would distract and heal me.

I found the owner and rented the place for$ 50 a month.The locals knew nothing about me. But slowly they started teaching me the art of being a neighbor. They dropped off blankets, tools and canned deer meat and began sticking around to chat. They would ask if I wanted to meet cousin Albie or go fishing. They started to teach me a belief in a different American dream, not the one of individual achievement but of neighborliness. Men would stop by with wild berries, ice cream or truck parts to see if I was up for courting. I wasn't, but they were civil anyway.The woman on that mountain worked harder than any I'd ever met. They taught me how to store food in the stream and keep it cold and safe._I_learned_to_keep_enough_for_an_extra_plate_for_company.

What I had believed in, all those things I thought were necessary for a civilized life, were nonexistent in this place.Up on the mountain, my most valuable possessions were my relationships with my neighbors.

After four years in that valley, I moved back into town. I saw a lot of people were having a really hard time, losing their jobs and homes. With the help of a real estate broker (房地产经纪人) I chatted up at the grocery store, I managed to rent a big enough house to take in a handful of people. It's four of us now，but over time I've had nine come in and move on to other places from here. We'd all be in shelters if we hadn't banded together.