back n.后面；背脊；靠背；后背；后卫vt.支持；后退adv.向后地adj.向后的；后面的；偏远的；过时的；积欠的
off adv.表示状态的关闭或离开prep.离开；在...之外adj.空闲的；离开的；关闭的v.离开；脱下
双语例句
He knew his son's classroom was on the left back corner of the ground floor, so he went there quickly and began to dig. 他知道儿子的教室在一层楼的左后角处，便疾步走到那里，开始动手。
