C,equivalent to whether.
The only thing you need to take care is B which is a wrong answer because you can't use it for a temparary action like go,come.If you want to use it,Fine.But it would be:
Mum,could you please tell me hong long Dad has been to London?
Hope this make sense to you!Cheers.
BTW,I think it should be "could you please tell me..." instead of "could you tell please me."