The difficulty appears when there is no natural choice of elements from each set.

Wood was the natural choice, but he declined the job for several reasons.

A career in medicine seemed a natural choice for me.

They saw us as a natural choice to work with.

"With the movie theater next door to us, it was a natural choice," she said.

Cycling should be a simple, easy and natural choice for getting around in an urban area.

That in turn him made a natural choice to help develop the space telescope.

It would seem a natural choice, given the new realities.

Thus he was a natural choice for the special diplomatic team.

As such, he was a natural choice for member of parliament.