阅读理解。 If you can read a clock, you can know the time of the day. But no one knows what time itself is. One way to think about time is to imagine a world without time. But there could be no movement, because time and movement cannot be separated. In early human history, the only changes that seemed to repeat themselves evenly were the movements of objects in the sky. The most easily seen result of these movements was the difference between light and darkness. The sun rises in the eastern sky, producing light. It moves across the sky and sinks in the west, causing darkness. The appearance and disappearance of the sun was even and unfailing. The periods of light and darkness it created were the first accepted periods of time. We have named each period of light and darkness one day. People saw the sun rise higher in the sky during the summer than in winter. They counted the days that passed from the sun’s highest position until it returned to that position. They counted 365 days. We now know that is the time Earth takes to move once around the sun. We call this period of time a year. They also developed a way to use the changing faces of the moon to tell time. The moon was “full” when its face was bright and round. The early humans counted the number of times the sun appeared between full moons. They learned that this number always remained the same---about 29 suns. We now know this period of time as one month. Early humans hunted animals and gathered wild plants. They moved in groups or tribes form place to place in search of good. Then, people learned to plant seeds and grow crops. As hunters, people did not need a way to measure time. As farmers, however, they had to plant crops in time to harvest them before winter. They had to know when the seasons would change. So, they developed calendars. No one knows when the first calendar was developed. But it seems possible that it was based on moons, or lunar months. 1. The underlined word “unfailing” (in para.2) is closest in meaning to '_____'. A. reliable B. everlasting C. limited D. changing 2. Which of the following is NOT the method early people used to tell time? A. Sun position B. Sun lightness C. Moon shape D. Planting crops 3. Why did people invent the first calendar to measure time? A. Because early humans hunted animals and gathered wild plants. B. Because early farmers had to grow and harvest crops in time. C. Because early people had to search for food in groups. D. Because early humans moved in groups or tribes from place to place. 4. Which of the following is TRUE? A. Why early people developed calendars is not clear B. When the first calendar was developed remains unknown. C. What early people based the first calendar on is certain. D. How early people counted a day is still unknown. 5. It can be concluded from the text that ______. A. time and movement are loosely related even at present days B. the light and darkness differences of the sun were the only movements in sky C. the period of twenty-nine suns is called one month D. early humans first accepted periods of time created by the moon.