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The development of the first calendar was probably based on ______.
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Text 1 If you are tired of watering your plants every day, you might want to try growing them right in the water. And in fact this is not a new idea: People in ancient Egypt were growing plants without soil more than 2,000 years ago. Moreover, the floating gardens of the Aztecs in early Mexico are another ancient example of gardening without soil. Nowadays this technique is widely used. It is called hydroponic gardening. Literally, the term hydroponics means cultivating in water rather than in soil, and in fact normal soil is not used in this process. But plants are plants, and so the concerns of the hydroponic gardener are really much the same as those of any other farmer. Even when they do not grow in soil, all plants need food, stability, oxygen, and protection from disease. The main nutrients required by plants are nitrogen, potassium, and phosphorus. Also, small amounts of other elements are needed. In the ancient hydroponic gardens of Egypt and Mexico, the growers had to rely on minerals that occurred naturally in the water. In modem hydroponic applications, workers carefully add these important minerals to pure water; in this way, the balance of waterborne nutrients can be controlled, depending on the kind of plants being grown and on the speed of growth of the crop. Plants usually get stability from the soil around their roots. Obviously, water cannot provide this. Plants farmed hydroponically are supported either by growing through a mesh over the Water, or by sinking their roots into sand or pea-sized gravel soaked in water. Either way, the plants stay upright, with their leaves exposed to the sun. They need no soil because, in this system, they do not derive nutrients from the medium that gives them stability. Oxygen is another essential requirement. The roots as well as the leaves of all plants must be able to breathe. If insufficient oxygen reaches its roots, a plant will die. To fulfill this need, hydroponic farmers usually keep the nutrient water flowing all the time. As the water circulates, it is aerated by splashing from one container to another: The splashing process increases the amount of absorbed air in the water. Finally, plants need a healthy environment. Especially when plants of the same species are grown close together, there is a real danger that diseases may spread quickly. A very clean growing medium will reduce this risk. Soil, the natural planting medium, may contain many harmful diseases or pests, but hydroponic gardening does not use soil. Starting with pure water and clean sand or gravel, the hydroponic gardener avoids many uncertainties. In these ways, hydroponics can overcome important agricultural challenges. For instance, hydroponic farming is able to produce worthwhile crops in regions where the soil is too poor for ordinary gardens, or where the supply of water is too scarce for normal irrigation. Also, even in fertile areas, hydroponic greenhouse makes it possible to cultivate small areas extremely densely: This can be very profitable during winter in cold climates, such as Canada or the Northern United States. Such considerations may not have mattered to the ancient Egyptians or Aztecs, but they are the basis of a thriving hydroponics industry today. Which word is closest in meaning to "fertile" (Paragraph 7)
炉火的微光渐渐地暗了下去，外面变黑了。我站起来要走，她拉住我，一面极其敏捷地拿过穿着麻线的大针，把那小橘碗四周相对地穿起来，像一个小筐似的，用一根小竹棍挑着，又从窗台上拿了一段短短蜡头，放在里面点起来，递给我说：“天黑了，路滑，这盏小橘灯照你上山吧!”我赞赏地接过来，谢了她。她送我到门外，我不知道说什么好，她又像安慰我似的说：“不久，我爸爸一定会回来的。那时候我妈妈就会好了。”她用小手在面前画一个圆圈，最后按到我的手上：“我们大家也都好了!”显然地，这“大家”也包括我在内。我提着这灵巧的小橘灯，慢慢地在黑暗潮湿的山路上走着。这朦胧的橘红的光，实在照不了多远，但这小姑娘的镇定、勇敢、乐观的精神鼓舞了我，我似乎觉得眼前有无限光明! 这段交代的记叙要素有（）
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