Do you know who the pen belongs to?belong后为什么加s?
问题描述：
Do you know who the pen belongs to?belong后为什么加s?
答
翻译：你知道这支钢笔是谁的吗?
who the pen belongs to是宾语从句,作know的宾语,宾语从句是主语是the pen,所以谓语动词belong加S.belong to 表示“属于”,是固定搭配.