※ in the house 指在房子里面。如：　　

Have you any valuables anywhere else in the house? 你房子里其他地方還有貴重物品嗎?　　

There were few dry eyes in the house when I finished. 我說完后房間里沒幾個人不掉淚的。　　

When Ann arrived home that night, she found Brian in the house watching TV. 那晚安回到家時，看見布賴恩正在屋子里看電視。　　

※ at the house 是指在房子那兒，可以在其前面、或后面、或旁邊等，換句話說，at the house 是指把 house 看作一個“點”。如：　　

At this moment a car stopped at the house. 就在這時，一輛轎車在房前停下了。　　

A market researcher called at the house where he was living. 一位市場調查人員造訪了他的住處。　　

哦！原來這么深奧！太感謝了！回答得及時詳盡又全面！辛苦啦！