But then, it was a reasonable question for either of them to ask.

Well, it seemed like a reasonable question to ask him.

It was a reasonable question and one for which neither of them had an easy answer.

These are reasonable questions, but the answer in each case has to be 'no'.

Here is one possible answer to that very reasonable question.

It was a reasonable question, and apparently not the one she'd expected.

Why he continues to do it is a reasonable question.

But for a long time, many people thought the same thing, so it's a very reasonable question to ask.

That was easily the most reasonable question asked so far today.

This is a question, or rather, these are two very reasonable questions.