B )3.Thomas discovered that problem A.with chance B.by accident C.with mistake D.by purpose A )4.When you leave the room,make sure the door A.is locked B.locked C.was locked D.lock 导航页导航页 ( )3.Thomas discovered that problem . A.with chance B.by accident C.with mistake D.by purpose ( )4.When you leave the room,make sure the door . A.is locked B.locked C.was locked D.lock B A