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.

Let me give you an 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.
The answer to this example can be: How many books are there in the British Library?
Here is why: In the Article, 10,000,000 is mentioned for the number of books available in the British Library, so this is a good question.

OK. solve this:
Article: Special trees that grow faster, fight pollution, produce better wood, and even sense chemical attacks are being planted by scientists in the US. When 40 per cent of Hawaii's US$14 million-a-year papaya industry was destroyed by a virus five years ago, work began on creating genetically engineered trees. Researchers successfully introduced seeds that were designed to resist the virus.Since then, more and more people have been testing genetically engineered trees.Some researchers put special bacteria into trees to help them grow faster and produce better wood.Others are trying to create trees that can clean polluted soil.Meanwhile fruit farmers are looking for trees that are strong enough to resist worms, and paper companies want trees that produce more wood and therefore more paper. The Pentagon even gave the researchers US$500,000 this year after they developed a pine tree that changes its colours if it senses a chemical attack.So far, the poplar, eucalyptus , apple and coffee trees are among those being engineered.All this can be done today because we have a better understanding of tree genomes . However, some people fear that the genetically engineered trees will cause dangerous results.They are worried that the new trees will breed with natural species and change the balance of the forest environment. "It could be destructive," said Jim Diamond, an environmentalist. "Trees are what is left of our natural environment and home to many endangered species." But researchers insist that science could give nature a fighting chance against both natural and man-made dangers.They hope to answer the critics by stopping the new trees from breeding, so their effect on the environment can be controlled.
Answer: Trees that can protect themselves at a chemical attack.
Answer:
Which kind of tree is not the ones that scientists are planting in the US?