题目解析:
题干下列哪一项最好地描述了第4段的组织结构?D正确,它的开头句提到了一个重要的发展,指的就是replacing some of their sand-flat rice fields with fishponds,段落的其余部分描述了构成其基础的系统。即指鱼塘和果树之间如何互利的;A错,summarizes the previous paragraph总结前一段没有,new developments.新发展也没有;B错 how a problem was solved没提到问题和解决方案;C错,错在后半句or why the development failed to last.为什么没发展起来是错的