despite much research,there _____still certain elements in the life cycle of the insect
问题描述：
despite much research,there _____still certain elements in the life cycle of the insect
that ____not fully understood.A is,isB is,areC,are,is Dare,are
答
选C 前面的elements 复数形式 用 are 后面 的life cycle 用单数应该 后面是insect用单数吧哦对对 是的不好意思 下面看掉了insect是一个大的种类