You bet 不是应该是“打赌”吗？错了，这里是“当然”。小事一桩也可以说成是 as easy as pie哦！还有更多地道口语表达，我们一起来看看吧！
小事一桩。
That’s a piece of cake.
That’s as easy as pie!
I can do it with my eyes closed.
不要告诉别人。
Don’t tell anybody (about it).
This is just between you and me.
This doesn’t leave this room.
This is for your ears only.
当然
You bet. （同意对方说法时用，“一点也没错”的意思）
You know it.
You betcha.
你在开玩笑。
You are kidding (joking).
You have got to be kidding (joking).
Are you kidding (joking)?