One vs A

[Offroad]

Dear teachers

Which one of these sound better?

It has been 3 days since they left. One/A possible explanation is that they are lost in the wood(s).

I honestly think neither of them reads quite well.

I would change it a bit:

It has been 3 days since they left. The most plausible possible explanation is that they are lost in the wood(s).

Very much appreciated

Offroad

 

[probus]

A possible explanation works, but I prefer one possible. The most plausible is also correct, but has a different meaning. One possible explanation is just that, one of many possibilities. But in using the most plausible you are singling out that explanation as the best one.

 

[Tdol]

One sounds natural to me too.