it's a piece of cake
口语·表达轻松完成
例句
Don't worry about the test, it's a piece of cake. I finished it in ten minutes.
典故来源
源自20世纪初美国，可能源于蛋糕分配游戏中轻松获胜的比喻，强调任务简单得像吃一块蛋糕。