Is this the book ________?
A.you are looking for itB.which you are looking forC.for which you are lookingD.that you are looking for it在线课程B
该句考查定语从句，将其变为陈述句式，结构会更清晰：This is the book________.该句意为“这是你在找的书吗?”首先排除A项和D项，因为定语从句中使用的it出现了逻辑意义的重复。look for是固定词组，动词和介词不可分开使用，介词不可提到关系代词之前。故答案为B项。