My brother bought me a lot of books he ________ useful to me．
A.regardedB.hoped themC.thought themD.considered在线课程D
he ________ useful to me是定语从句，he之前省略了作宾语的that或which，useful作宾语补足语。regard常与介词as搭配，表示“认为……是”；thought them中的them应去掉。故选D项。