Alright, lets give this another go.
I'm having trouble understanding the best way to respond to someone asking "why".
My study guide advised,
To answer the question with "why", make a statement sentence that indicates the reason and add からです at the end,
A:どうして昼ご飯を食べなかったんですか B: ダイエットをしているからです
Feeling like it couldn't possibly be that simple, I went looking to see if anyone had explained things in more detail. However, nearly everything I found was on から in sentences that described both the cause and response, seemingly without being asked, such as
あのラーメン屋は人を待たせるから、行かないことにした。
I haven't been able to find much at all on からです in direct response to a question, as it was in my book's example.
I figured the most likely reason for this was either
A, からです is a nonstandard approach and my book is weird, or
B, I've missed something.
Unfortunately, B prompted me to wonder if some of these descriptions actually were a direct response that I was misunderstanding.
So that while I was searching for something like
A:どうして外に行かなかったんですか
B： 雨が降っていたからです
People were actually saying
A:どうして外に行かなかったんですか
B： 雨が降っていたから、外に行きませんでした
I explain this mostly because I know how little sense I made the last time around, and I'm filled with shame and mild amusement.
My question is,
Is something like "ダイエットをしているからです" actually a standard way to give a reason in response to a question? If not, what would be more appropriate?
Any other ways to give a reason are welcome, because nuance is neat.
Thank you for your patience, I hope this is a little more clear.
