Choose the best answer for (15)
"Daniel is a person who loves to be outdoors. When he was young, he skied a lot. Every winter he went to his grandfather's house in the mountains ...(13)... he skied. Skilling in not his only outdoor ...(14).... Daniel also loved to run and play tennis. ...(15/1)..., a couple of years ago, he ...(15/2)... a knee operation. ...(16/1)... this, she stopped ...(16/2)... marathons for a while. These days he has been running marathons again. His knee is much better, and he also could play tennis daily."
