Two years ago, three scientists traveled to the Antarctica to explore a secret world hidden _________ the ice.
In no country other than Britain, it has been said, ____ experience four seasons in the course of a single day.
They have no idea at all ____.
________ on the top of the mountain is an ancient tower dating back to hundreds of years ago .
No sooner _____ themselves in their seats in the theatre _______ the curtain went up.
Only when _______ .