题目

阅读下面材料，在空白处填入适当的内容(1个单词)或括号内单词的正确形式。Modern mammals, including humans, owe their sharp sense of hearing 【1】 three tiny bones in the middle ear that were absent in their reptile ancestors, but the point at which this transformation 【2】( occur) has remained unclear.Scientists have now identified the transitional stages in the remains of a 【3】( new) discovered species that lived 125 million years ago in 【4】 is now northeastern China: effectively a missing link in the evolutionary chain. Their 【5】( find) were publ海平面上升对该地带的影响有（　　）①加剧农田土壤盐碱化 ②滩涂面积减少 ③淹没部分耕地 ④有利于港口基础设施建设． A、①②B、②③C、③④D、①④