同学你好，该知识点来自沪江网校《新概念英语2、3、4册连读【双11专享班】》的课程，想要更系统的学习，欢迎进入课程学习。不仅可以和更多的同学一起学习，而且还有老师、助教随时的学习指导和知识点解答哦。

同学你好～

这句话补充完整以后是Could you please confirm the date (which) we have settled down,  这里省略了关系词which, we have settled down是修饰the date的定语从句。

[w]settle down[/w] 一般有以下四种用法：

1．have a regular place to live and a regular job；begin a normal，stable life 生活和工作安顿下来；安居乐业
John will settle down after he gets a job and gets married．约翰在找到工作并且结婚以后才会安顿下来。
Many people settle down in San Diego because of the fine weather．许多人在圣地亚哥安居下来，因为那儿的气候宜人。

2．become calm，quiet or peaceful 安静下来
The house settled down for the night after the children were put to bed．夜晚孩子们被安顿上床后，这所房子就平静下来了。
The children settled down when their teacher entered．老师进来以后，孩子们就安静下来了。

3．begin to concentrate on 开始专心于
There were so many distractions that we were unable to settle down to studying．有那么多令人分心的事，我们无法安下心来学习。

4．sit or lie comfortably 舒服地坐着或躺下
She settled down in the back of the car and fell asleep quickly．她舒服地坐在汽车后座上，很快就睡着了。

而且settle down都是不及物的用法，后面是不能直接接宾语的，所以助助认为settle down the date不对，而且也没有查到词典上有此用法。助助指查到了settle on/upon a date, 决定一个日期，没有settle down the date的用法。

所以这里，我们只能理解为，settle本身作为及物动词可以直接接宾语，表示“确定，决定”， 然后把down看成个介词，理解为settle the date down。

希望助助的回答可以帮到你～祝你学习进步～