动词
中文翻译：保持
同义词：
['maintain', 'preserve', 'sustain']
例句：
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1. We need to keep the windows closed to stop the cold air from coming in.
我们需要关紧窗户，以防止冷空气进来。
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2. The old house needs to be kept well-maintained to prevent it from falling down.
这所老房子需要好好维护，以防倒塌。
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3. She kept her promise and returned the borrowed books on time.
她履行了承诺，按时归还了借来的书籍。