China's first and only Grand Slam winner Li Na formally announced her retirement on Friday, leaving the Chinese tennis yearning for the next superstar. Following is part of her farewell and retirement letter: For close to fifteen years, we've been a part of each other's lives. As a tennis player representing China on the global stage, I've trekked  around the world playing hundreds of matches on the WTA tour, for China's Fed Cup team, at the National Games and at several Olympic Games. You've always been there for me, supporting me, cheering me on, and encouraging me to reach my potential. Representing China on the tennis court was an extraordinary privilege and a true honor. Having the unique opportunity to effectively bring more attention to the sport of tennis in China and all over Asia is something I will cherish forever. But in sport, just like in life, all great things must come to an end.2014 has become one of the most significant years in my career and my life. This year was full of amazing highlights, which included winning my second Grand Slam singles title at the Australian Open and sharing the extraordinary experience with my country, my team, my husband and my fans. It was also a year filled with difficult moments, such as having to deal with the inevitable - making the decision to end my professional tennis career. The amazing moment in Australia was filled with joy, happiness and extraordinary sense of accomplishment. It took me several agonizing  months to finally come to the decision that my chronic  injuries will never again let me be the tennis player that I can be. Most people in the tennis world know that my career has been marked by my troubled right knee. The black brace I wear over it when I step on the court has become my tennis birth mark. After four knee surgeries and hundreds of shots injected into my knee weekly to ease swelling and pain, my body is begging me to stop the pounding. My previous three surgeries were on my right knee. My most recent knee surgery took place this July and was on my left knee. After a few weeks of post-surgery recovery, I tried to go through all the necessary steps to get back on the court. One of my goals was to recover as fast as I could in order to be ready for the first WTA tournament in my hometown of Wuhan. As hard as I tried to get back to being 100%, my body kept telling me that, at 32, I will not be able to compete at the top level ever again. What is the real reason for Li Na to end her professional career?
Her crazy fans. Her painful injuries. Her supporting family. Her old age.
Question: China's first and only Grand Slam winner Li Na formally announced her retirement on Friday, leaving the Chinese tennis yearning for the next superstar. Following is part of her farewell and retirement letter: For close to fifteen years, we've been a part of each other's lives. As a tennis player representing China on the global stage, I've trekked  around the world playing hundreds of matches on the WTA tour, for China's Fed Cup team, at the National Games and at several Olympic Games. You've always been there for me, supporting me, cheering me on, and encouraging me to reach my potential. Representing China on the tennis court was an extraordinary privilege and a true honor. Having the unique opportunity to effectively bring more attention to the sport of tennis in China and all over Asia is something I will cherish forever. But in sport, just like in life, all great things must come to an end.2014 has become one of the most significant years in my career and my life. This year was full of amazing highlights, which included winning my second Grand Slam singles title at the Australian Open and sharing the extraordinary experience with my country, my team, my husband and my fans. It was also a year filled with difficult moments, such as having to deal with the inevitable - making the decision to end my professional tennis career. The amazing moment in Australia was filled with joy, happiness and extraordinary sense of accomplishment. It took me several agonizing  months to finally come to the decision that my chronic  injuries will never again let me be the tennis player that I can be. Most people in the tennis world know that my career has been marked by my troubled right knee. The black brace I wear over it when I step on the court has become my tennis birth mark. After four knee surgeries and hundreds of shots injected into my knee weekly to ease swelling and pain, my body is begging me to stop the pounding. My previous three surgeries were on my right knee. My most recent knee surgery took place this July and was on my left knee. After a few weeks of post-surgery recovery, I tried to go through all the necessary steps to get back on the court. One of my goals was to recover as fast as I could in order to be ready for the first WTA tournament in my hometown of Wuhan. As hard as I tried to get back to being 100%, my body kept telling me that, at 32, I will not be able to compete at the top level ever again. What is the real reason for Li Na to end her professional career?
A. Her crazy fans.
B. Her painful injuries.
C. Her supporting family.
D. Her old age.
Answer: