I picked up the kids' clothes that were lying on the floor.

picked 是动词 pick 的过去式，pick 的意思是"拾起、挑选"。 up 是副词，表示"向上"的动作方向。 pick up 是一个常用短语动词，意思是"捡起、拾起"，也可以表示"接人"或"学会"等含义。