首先，先看看一个老师对一个句子的讲解和分析。

“A modern hard-core sociobiologist might even go so far as to claim that this aggressive instinct evolved as an advantageous trait， having been of survival value to our ancestors in their struggle against the hardships of life on the plains and in the caves， ultimately finding its way into our genetic make-up as a remnant of our ancient animal ways. ”这个句子也快要达到5行的长度，但仔细研究会发现：“modern”和“hard-core”都是对sociobiologist的修饰;紧接着后面实际上是“so … as”的结构;“that”引导的宾语从句之中，“having”和“finding”显然是现在分词作为状语，其逻辑主语依然是宾语从句中的主语 “instinct”。单独如果写一个句子“Being a vegetarian， she does not eat any meat. ”，应该许多考生在理解上都没有问题;但是上述句子中本身结构就已经很复杂，最后还是两个现在分词并列，就未必所有考生都能一次看懂了。