backn.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backchatn.回嘴；顶嘴；机智的对答=back talk(美).

1. 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。