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They operate at extremely high efficiency, and their main by-product is water.
这种电池的使用效率极高，而主要的副产品只是水。
youdao
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It is also a main by-product of biodiesel production.
它也是生物柴油生产中主要的副产品。
youdao
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It is also a main by-product of biodiesel production.
它也是生物柴油生产中主要的副产品。
youdao