Unit 6270 collect v.搜集,堆积,收集271 shell n.贝壳,壳,外形; v.去壳,脱落272 marathon n.马拉松,耐力的考验273 skate n.冰鞋,溜冰鞋; v.滑冰,溜冰274 pair n.一双,一对,副; v.使...成对275 since prep.自从276 Hi...