"What possible explanation do you have for watching my house?"

This had long seemed like a possible explanation to me.

It was the only possible explanation for what had happened.

At least that was one possible explanation for their action.

There's no possible explanation for what just happened here, so we're not going to make one.

Over the next few weeks a number of other possible explanations were put forward.

However, there is at least one possible explanation I can offer.

There are a number of other possible explanations for their success.

"There's no possible explanation for a cold space in the middle of air!"

They'd come up with possible explanations for everything else, but not that.