虽然对大多数历史学家来说，根据重要性对历史原因进行排序的必要性似乎是显而易见的，但这种等级制度引发了严重的哲学难题。

While the need to rank historical causes in some order of importance may seem obvious to most historians, such hierarchies raise serious philosophical difficulties.

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然而，很少有人意识到基本技能的重要性。如图所示，班上的学生正在质疑学习诸如乘法表这样的基本技能的必要性。

However, few people realize the importance of basic skills. As is shown in the picture, the pupils in the class are questioning the necessity of learning basic skill such as multiplication table.

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本文首先介绍了采砂船监测系统的开发背景以及相关技术，得出研究本课题的重要性和必要性。

Fristly, this article introduces the developed background and key technology, educes the importance and necessarian of this article.

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