I would like a ask a very small question -
He asked a riddle which I was unable to solve.
I am confused whether I would put a comma before 'which' or not. Putting a comma before which sounds ok and in fact, the sentece looks good, but, not using comma doesn't make it absurd either. What I am asking is, should I write -
He asked me a riddle, which I was unable to solve. or He asked me a riddle which I was unable to solve.
The first one sounds better to me, however I am unsure of any rule which supports my opinion.