as to the reason

[Chicken Sandwich]

From Cambridge Certificate of Proficiency in English 2:
Complete the second sentence so that it has a similar meaning to the first sentence, using the word given.

It was never explained why Gregor decided to leave.

No . . . . . . . . . . . . . . . . . . . . . of Gregor’s decision to leave. (given)

Would you accept, ‘No explanation was ever given as to the reason of Gregor’s decision to leave.’?

The book suggests, ‘No explanation was ever given as to the reason of Gregor’s decision to leave.’

However, would it be OK to include “as to the reason” as wordy version of “why”? Or is "as to the reason" completely redunant here?

Thank you in advance.

[emsr2d2]

An explanation means "to give the reason" for in some contexts so I would say it was redundant.

No explanation was ever given for Gregor's decision to leave.

As you can see, I would have changed "of" to "for" but as "of" was in the original, that wasn't possible.

[Chicken Sandwich]

As you can see, I would have changed "of" to "for" but as "of" was in the original, that wasn't possible.

Would you always say "explanation for" instead of "explanation of"? I agree with you, but the Longman Dictionary of Contemporary English says that you can say either (see explanation - Definition from Longman English Dictionary Online, definition #1), but I'm not sure if the choice depends on context or on personal preference.

[bhaisahab]

Would you always say "explanation for" instead of "explanation of"? I agree with you, but the Longman Dictionary of Contemporary English says that you can say either (see explanation - Definition from Longman English Dictionary Online, definition #1), but I'm not sure if the choice depends on context or on personal preference.

It depends on context IMO, and, in the context of your original sentence, I would use "for".