Over on Quora recently, someone asked the community for a "brain teaser that is very short and extremely hard for adults".
Thankfully, up stepped Peter Flom, who appears to have a PhD in psychometrics, with this belter:
The [blank] doctor was [blank] to operate because he had [blank].
Fill each blank with the same letters in the same order to make a sentence that is both sensible and grammatically correct.
The puzzle has been perplexing people ever since, with answers ranging from as far as "PREPARED. It's PREPARED." to "qualified".
Both are wrong. So can you work out the answer? Scroll down to find out...
It appears as though a man called Stan Belot has turned up with the answer:
It seems to work:
The notable doctor was not able to operate because he had no table.
Are there any alternatives? Let us know in the comments...