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.
One 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 is here: How many books are there in the British Library?
Explanation: 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: Article: When Juliet was a child, she often went to the city park and played with her friends. On a sunny morning, when Juliet came to the park with her mum, she looked around and felt very unhappy. "What's the matter, dear?" asked her mum. Juliet replied, "Mum, there's so much trash on the ground." Juliet's mum looked around. There was paper, boxes and glass bottles everywhere. "What can we do?" asked Juliet. "I'm sure you will think of something," said her mum. As soon as Juliet and her mum went home, Juliet painted a picture of the park and wrote a sign in large black letters at the top of the picture. The sign read "PLEASE KEEP OUR PARK CLEAN". Later, she took plenty of bags and went back to the park with her mum. Juliet put up her picture on a big trash can . "Will you help me pick up the trash, Mum?" Juliet said as she handed her mum a bag. "I sure will," replied her mum. The children at the park ran over to see what was going on. Juliet handed them each a bag. "Let's clean this place up," said Juliet. Then they began to pick up the trash, talking and laughing. Soon all the bags were full. "We need to come back another day. There's still some trash on the ground, but the park looks much better," said Juliet. Her mum said, "So it does. _ "
Answer: Because there was too much trash at the park.
Solution:
Why was Juliet sad?