历史学家认为，19世纪一再发生的蝗虫入侵改变了美国密西西比河以西的农业格局。

Historians credit repeated locust invasions in the nineteenth century with reshaping United States agriculture west of the Mississippi River.

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有效的决策人，首先要辨明问题的性质：这是一再发生的经常性问题呢，还是偶然的例外？

The first question the effective decision - maker asks is: "is this a generic situation or an exception?"

youdao

有效的决策人，首先要辨明问题的性质：这是一再发生的经常性问题呢，还是偶然的例外？ ！

Thee first question the effective decision-maker asks is:"Is this a generic situation or an exception?""

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