断句是理解和分析长难句的关键步骤，以下是一些基本的断句原则和步骤：

断句原则

长度适中 ：将句子划分为长度大约为10个词的部分。

语法结构完整：

每个断点后的部分应是一个语法结构完整的句子。

断句步骤

寻找标点符号

逗号：分隔并列成分、插入语、定语从句等。

冒号：前后通常是两个完整的句子，冒号后的句子对前面的进行解释。

分号：表示并列关系。

识别连词

从属连词（如that, which, who等）：用于连接从句，找到从句的起始和结束位置进行断句。

并列连词（如and, or, but等）：用于连接并列句或并列部分。

处理短语

介词短语、分词短语、不定式短语等：利用这些短语进行断句，简化句子结构。

示例分析

以句子 "This trend began during the Second World War, when several governments came to the conclusion that the specific demands that a government wants to make of its scientific establishment cannot generally be foreseen in detail." 为例：

标点符号

逗号："This trend began during the Second World War,"

分号："when several governments came to the conclusion that..."

连词

从属连词 "when"："when several governments came to the conclusion"

从属连词 "that"："that the specific demands that a government wants to make of its scientific establishment cannot generally be foreseen in detail."

短语

不定式短语 "to make of"："demands that a government wants to make of its scientific establishment"

通过以上步骤，可以将长句断句为几个易于理解的短句。

总结

断句时，应遵循长度适中和语法结构完整的原则，利用标点符号、连词和短语作为断句标志。理解句子结构后，再去除不影响理解的修饰成分，如插入语、副词等。