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In this task, you're given an article and an answer. Your task is to generate the fill-in-the-blank question for this answer based on the given article. The blanks are always at the end of the question, and can be filled with more than one word or phrase.
question:
Article: We all enjoy the colors of autumn leaves. Did you ever wonder how and why a fall leaf changes color? Where do the yellows and oranges come from? To answer those questions, we first have to understand what leaves are and what they do. Leaves are nature's food factories. Plants take water from the ground through their roots. They take a gas called carbon dioxide from the air. Plants use sunlight to turn water and carbon dioxide into glucose, which is a kind of sugar. Plants use glucose as food for energy and as a building block for growing. The way plants turn water and carbon dioxide into sugar is called photosynthesis, which means " putting together with light. " A chemical called chlorophyll helps make photosynthesis happen. Chlorophyll is what gives plants their green color. As summer ends and autumn comes, the days get shorter and shorter. This is how the trees "know" to begin getting ready for winter. During winter, there is not enough light or water for photosynthesis. The trees will rest, and live off the food they stored during summer. They begin to shut down their food-making factories. The green chlorophyll disappears from the leaves. As the bright green fades away, we begin to see yellow and orange colors. Small a-mounts of these colors have been in the leaves all along. Covered up by the green chlorophyll, we just can't see them in summer. The bright reds and purples we see in leaves are made mostly in the fall. In some trees, like maples, glucose is trapped in the leaves after photosynthesis stops. Sunlight and the cool nights of autumn cause the leaves turn this glucose into a red color. The brown color of trees like oaks is made from wastes left in the leaves. It is the combination of all these things that make the beautiful colors we enjoy in the fall.
Answer: introduce the topic of the passage
answer:
The writer asked two questions in the beginning in order to_.

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Article: Of all nature's disasters, forest fires are often considered the most frightening. Moving at lightning speed, huge walls of flames can burn acres of land in just a few minutes. And although technology, including the use of tire-retardant chemicals, has greatly helped the fight against forest fires, they still take great damage. According to the National Interagency Fire Center, the fire season last year was the worst on record in terms of the number of fires and acres burned. There were 96.385 fires and9,873429 acres affected by fire in a year that was 125% more destructive than the 10-year average . These fires cost the federal govemment $1.5 billion to fight, and this figure does not include the money spent by local and state govemments as part of the effort. Fires in the southern states represented half of the national total last year. with Texas. Oklahoma and Arkansas being home to an usually high amount of activity. Wildfire have also taken place in Western states such as California, Colorado. and Alaska throughout the past 10 years. It is said that two-thirds of forest fires are started accidentally by people. almost one quarter are purposely set, while lighting causes 10%. Forest fires can have advantageous effects. Charcoal enriches soil, and some plant species grow well after. The cones of the jack pine tree, for example, will not spread their seeds unless there is heat. Douglas fir trees grow best in open sunlight areas after fire.
Answer: they spread too fast and make great damage.
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Forest fires are considered to be the most frightening because _ .

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Article: Many people think walking is a good way to exercise and many fat people are advised to lose weight by walking. In fact, you can do it everywhere. Here's how to prepare for walking: ^Find a pair of shoes. It is easy to find a pair of shoes, but what matters most is comfort. ^Check your shape. The following tips will help you stay comfortable and get the most out of your walk: * Stand up straight. Imagine a string pulling you up from the center of the top of your head. Let that string pull you up as straight as possible. Relax your shoulders. * Look ahead. Keep your neck straight and your head held high to avoid unnecessary strain to your neck and shoulders. If you have to look down to see where you're going, lower your eyes, not your head. * Move your arms. Bend your elbows and let your arms swing naturally at your sides. You'll burn up to 15 percent more calories by keeping your arms moving. ^Stay safe walking is one of the safest activities you can do. Still, it's wise to take a few precautions . * If you're walking at night, wear a piece of reflective clothing. * When the weather's warm, be sure to drink a tall glass of water before you set out and another when you return. * If your path is rough, protect your ankles. Wear a comfortable elastic bandage for support, and keep your eyes focused on the path.
Answer: lower your eyes
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You are advised to _ to see where you are going during walking.