A questionable story.
A questionable reputation.
Of questionable excellence.
It is questionable if the universe is open or closed.
Tiffiny's behavior is highly questionable.
Other insects visit the flower with more questionable result.
One morning, while Carmen was cleaning the house, he caught her standing in the living room, confronting the recliner with a questionable amount of courage.
It is questionable if the substance in question is mucoid.
How much old tradition underlies these stories is questionable.