I don’t know who invented _____ iPhone, but I think it is____ useful invention.
Tony was very unhappy for _______ to the party.
The research is so designed that once _______ nothing can be done to change it.
After graduation she reached a point in her career __________ she had to decide what to do.
Edward, you play so well. But I ________ you played the piano.
Not until I began to work ________ how much time I had wasted.