1a. I obviously don’t know the answer what happened.
1b. I obviously don’t know the answer exactly what happened.
1c. I obviously don’t know the answer as to exactly what happened.
1d. I obviously don’t know the answer about what happened.
1e. I obviously don’t know the answer about what happened exactly.
Please correct the above.
Thanks.
1a I obviously don’t know the answer regarding/as to what happened.
1b I obviously don’t know the answer regarding/as to exactly what happened. (as 1c)
All the sentences sound stilted and awkward with the unnecessary inclusion of ‘the answer’.
They can be replaced by the following.
I obviously don’t know the answer.
or
I obviously don’t know (exactly) what happened.