5.by构成的短语 (1) 偶然;无意中;不小心 (2) 错误地 (3) 故意地 6.spot vt.发现;认出 n.污点;斑点;地点 (1)spot sb. sth. 看到某人正在做某事 (2) the spot=on the scene到(在)现场;当场
by accident=by chance
by mistake
by design=on purpose
doing
on