阅读下面短文，从短文后各题所给的A、B、C和D四个选项中，选出可以填入空白处的最佳选项。
I was having a period of bad health. I had one operation after another. I was falling 1 faster than the doctors could put me back together. But I just couldn't bear the operation, the hospital stay, the long recovery and the physical therapy（康复治疗）. I told my doctor I was going to try 2 else.
I'd discovered that walking gave me a little 3. So I started walking. The first day, my wife 4 off our steep Silver Lake hill to a flat street. She got me out of the car, and I walked about two blocks 5 asking to be taken home. The next day, I walked about four 6.
Slowly, feeling a little 7 every day, I began to walk a mile or more. I even 8some hills to my route. I became interested in the network of public stairways around Silver Lake I made a 9 of it and walked every public staircase in Silver Lake. That went pretty well, so I 10 onto Echo Park. I was feeling better, so I kept going. The search finally 11 “Secret Stairs: A Walking Guide to the Historic Staircases of Los Angeles' a book 12 in the spring of 2010. By then, I had 13. I'd been walking at least an hour a day for three years. My life 14 returned to normal.
In three years of walks, I've met dozens of people who'd had 15 experiences of rebirth or recovery. One man told me he'd lost 80 pounds walking the secret stairs and was dating for the first time in a decade. One woman told me she'd 16 knee operation. Another told me she'd been 17 to start ballroom dancing again.
All I'd 18 from the walks was relief from pain. What I got was 19, community and a whole new experience of my city. Out of the car, on my feet and moving at walking pace, I 20 Los Angeles for the first time.
