这个句子如果按正常语序安排，应该是——Many people / whosechances to do so were much inferior to Miss Martha's / have married.可见 whose chances to do sowere much inferior to Miss Martha's 是定语从句，但是这种安排中的主语部分显然比两个词的谓语部分 have married 长得多，是一种外头重脚轻的臃肿结构，为了是句子平衡所以就把定语从句拖后，变成如下的结构：
主句：Many people havemarried 许多人已经结婚定语从句：whose chances to doso were much inferior to Miss Martha's. --[主语] whose chances to do so）这些已婚人结婚的机缘【不定式 to do so 是 chances 的后置定语，是 to get married 避免重复的代用形式】 -- [谓语部分] were much inferiorto Miss Martha's. 远不如玛莎小姐的（结婚的机缘）【Miss Martha's 是名词所有格，后面省略了前文出现过的 chance to do so】