back[bAk]adj.后面的,在后面,早过去的,前(欠)的钱adv.向后地n.背部,后面v.后退,支持back[bAk]n.背,背部We lay on our backs under the tree.我们在树下躺着.She put the saddle on the horse's back.她把马鞍放在马...