雅思句子分析：两个并列句的复杂主语

It will never be known how and when this numeration ability developed, but it is certain that numeration was well developed by the time humans had formed even semi-permanent settlements. 难点解析 本句的难点在于两个并列句的主语比较复杂，找出it指代的内容是理解句子的关键(it作形式主语，how and when和that分别引导的两个主语从句是两个并列句的真正主语)。 英文中代词出现的频率非常高，理解代词指代的含义很重要。对这种类型的句子，用户不仅应该准确找出其指代关系，还应该能马上反应出其结构特点，并且将其运用到写作中。 句子分析 子句类型并列句 连 接 词无逻辑连接词 子句内容It will never be known something. 语法分析It [形式主语] will [谓语] never [状语] be known [谓语] something. [主语] 子句翻译某事永远不会被知道。 子句类型并列句 连 接 词BUT 子句内容It is certain something. 语法分析It [形式主语] is [系动词] certain [表语] something. [主语] 子句翻译某事是可以肯定的。 子句类型主语从句 连 接 词HOW AND WHEN 子句内容How and when this numeration ability developed. 语法分析How and when [状语] this numeration ability [主语] developed. [谓语] 子句翻译这种计数能力是如何以及何时开发的。