正文：
Definitely?
确定吗?
Are you sure?
你肯定吗？
Is there any doubt?
有什么疑问吗？
How can that be?
怎么会这样？

经典句扩展：
You couldn't have been mistaken, could you?
你不会弄错的，对吧?
Are you certain about his coming?
你确信他会来吗？
Perhaps I misunderstood, but are you sure what to do?
也许我误解了，不过你确实知道该怎么做吗？
Is there any room for doubt about it?
对此事有怀疑的余地吗？