Moreover, because microRNAs are so small and simple in structure, they can be manufactured for use as research tools.

此外，因为小分子核糖核酸的构造既小又简单，所以可以制造核糖核酸，把它当作研究工具来使用。

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Many cannot be manufactured in small towns because they can be made efficiently only in regions large enough to support substantial production.

许多却不能够在一些小城镇中生产，因为它们只能在足以支撑有实际价值生产的足够大的区域才能被有效率地制造出来。

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