"Ultimately, as Churchill concluded about Russia,
the key to unlocking the Korean riddle/mystery/enigma lies in the determining its national interest.'
If it were upto me, I would say
the key to unlock something, so why the -ing form here?
I usually say sentence like these:
The scientists believed that they have the key to unlock the mystery of the Pyramids. That lawsuit will be the key to open up a whole new national debate about marriage.Thank you.
