Although Gutman admits that forced separation by sale was frequent，he shows that the slaves’preference，revealed most clearly on plantations where sale was infrequent，was very much for stable monogamy.
请问老师，revealed most clearly on plantations where sale was infrequent，书上说这句是插入语，那样这算是过去分词短语作插入语吗？
插入语的剖析是一种懒惰的剖析，一见二个逗号隔开的结构就一句插入语打发了。这太草率了。本句中的过去分词短语显然是对前面名词的补充说明，是一个非限制性定语，等于which was revealed...。所以这个分词短语最好剖析为非限制性定语。非限拟定语本身就需要逗号隔开的。