This painting is so valuable that it is rather difficult to calculate _______ its price would be if the museum _______ to sell it.
It was the training _____ he had as a young man _____ made him such a good engineer.
It was not until he came back _____ he knew the police were looking for him.
I hate _____ when the light turns red and the people don’t move until it is about to turn green again.
______ today, he would get to Germany by Friday.
He was very busy yesterday, otherwise he ____ to the meeting.