It is not until recently ______ the scientists have found proof of there being water on Mars.
__ unemployment and crime are high, it can be assumed that the latter is due to the former.
______ the police thought he was the most likely one, since they had no exact proof about it, they could not arrest him.
hungry I am, I never seem to be able to finish off this loaf of bread.
____ caused the accident is still a complete mystery.
____ is a fact that English is being accepted as an international language.