Thief-turned-teacher

[Susam Pal]

A mathematics teacher narrated the most important story of his life
to his students one day, "Seven years ago, I was sentenced to an
unusual punishment after having been convicted of theft. I was taken
to a closed space with many doors in front of me. I was told that all
but one of them had hungry lions behind them. If I could open the one
without a lion behind it, I would be free. If I opened the wrong
door, I would be killed."

He continued, "Only the king knew which one of those doors would lead
me to freedom. He allowed me to ask two yes-no questions under the
condition that if I managed to get out that place alive, I would have
to serve his kingdom as a mathematics teacher for the rest of my
life. The king promised me that he would answer both the questions
truthfully if he knew the answers. In case he didn't know the answer
to a question, he would clearly say so. I was vey lucky. The number
of doors was just right. Had there been one more door, I might not
have got out of that place alive."

What two questions might he have asked?

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Originally posted at: http://cotpi.com/p/24/
Correct solutions will be archived at the cotpi link mentioned above.
Solutions to 'Sum of twin primes': http://cotpi.com/p/23/#responses