This is what's known as a subject question. When the focus of the question-word phrase - in this case 'Which things in the house' - is also the SUBJECT of the question, we don't need to use the auxiliary verb 'do'. Here are some similar examples: Who lives here? What happened? How many people came?

Hello Katherine, There are two different types of question in English. Subject questions and object questions. Object (things after the verb) questions normally have 'do'. (What do you like? - I like chocolate.) Subject questions (about things before the verb) do not have the auxiliary do. (Which things in the house belong to you? - The pictures, the carpets and the books belong to me.) Hope this helps Bob