Teacher: In this task, you're given an article and an answer. Your task is to generate the question for the answer based on the given article.
Teacher: Now, understand the problem? If you are still confused, see the following example:
Article: There are a lot of public libraries in Britain. These libraries have more than one hundred and fifteen million books, not including those libraries of public schools. Public libraries not only lend books, music records but also help children, patients in hospitals and others to get special play readings, film shows and so on. The first public libraries were founded in about the year 1850. Today's public libraries usually have a reading-room, a lending room and a reference room. The greatest and most famous library in Britain is that of the British Library in London. It was founded in 1973 and has over 10, 000, 000 books. It has nearly every magazine, newspaper and book published in Britain and other parts across the world.
Answer: 10,000,000 or less.
Solution: How many books are there in the British Library?
Reason: In the Article, 10,000,000 is mentioned for the number of books available in the British Library, so this is a good question.

Now, solve this instance: Article: (CNN)---NBA star Yao Ming announced his retirement during a news conference in China on Wednesday."I need to make a personal decision," Yao said."I am ending my basketball career. I am very grateful. I would like to thank my family members and my parents. And most of all, the Houston Rockets." Voted an All--Star player eight times while playing for the Houston Rockets, he was one of the most successful overseas players in the league. Yao has chalked up a career average of 19 points, 9.2 rebounds and 1.9 blocks . His field-goal percentage was 52.4. In recent years, however, he struggled with foot and ankle injuries, and missed the 2009-2010 seasons. He suffered a fracture on his left ankle, and missed last season after playing only five games. Yao has been undergoing treatment and training in recent months, but some doubted he could make a comeback. The 30-year-old said he struggled to learn English when he first came to the United States, and grew a lot during his time in the country. " 9 years ago, I came to Huston as a tall, skinny player. I grew to a man there. I also had my daughter there. I thank you all," Yao said during the packed news conference in Shanghai. Yao's retirement came the year as another NBA giant Shaquille O'Neal. Both seven-footers had battled for many years. Kobe Bryant said Yao opened up doors for Chinese players to feel they could play in the NBA."All that started with Yao," Bryant said.
Answer: Because he was seriously injured in his left ankle.
Student:
Why did Yao miss the 2009-2010 season?