A bee is a very useful insect.

蜜蜂是十分有益的昆虫。

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It can be useful to filter out external stimuli if you are writing an email in a noisy coffee shop, for example, or are searching for a camouflaged insect in a rainforest.

例如，要是你在在嘈杂的咖啡馆里写一封电子邮件或在雨林里搜寻一只伪装的昆虫，能过滤掉外部的刺激就很有用。

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The special differential staining methods for inclusion body of insect virus affords us a useful methods, which check up on inclusion body of insect virus under the light-microscope.

昆虫包含体病毒特异性的鉴别染色方法为我们准确地在光学显微镜下检查包含体病毒提供了有益的方法。

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The main goal of this research was to understand how insect flight works, rather than to build a useful robot.

BBC: Robotic insect: World's smallest flying robot takes off