congratulations!!!

[zoobinshid]

Hello everybody,
Would you please tell me what is the proper answer to this sentence?
A:congratulations!!!
B:?
1)for what?
2)what for?
3)on what?


Thanks in advance,

[Tdol]

I think you could use all of those.

[zoobinshid]

Thanks tdol,but doesn`t it make any difference to use them interchangeably?

[Casiopea]

To me, "on what" sounds more formal than the others. It side-steps the "why" and goes right to the "what". In other words, I know I deserve to be congratulated, but what I did to deserve that is unknown to me. Both "What for?" and "For what?" are synonymous with Why? To me, it sounds a tad bit more confident to assume the why and get right to the what. That's why I'd respond with, "on what?"

All the best.