选A"当我看见那些我小时候就熟悉的建筑被拆迁走的时,我感到有点低落."

　　先来分析一下这个句子：I(主语)was(谓语)alittledisappointed(表语)whenIsawtheoldbuildings(时间状从)【thatIhadknownasayoungboy(定从,修饰"buildings")】werenowgone.把括号内容删去,剩下：IwasalittledisappointedwhenIsawtheoldbuildingsweregone.这题就很简单了,考的是词组"seesth.bedone"(看见某物被.).选A.