It was the training ____ he had as a young man ____ made him such a good engineer.
He wondered __________ the pyramids were built.
He insisted that he __________ and that he ________ nothing wrong.
---It's reported__________the new underground line has been completed. ---Yes, but it hasn't been made clear ________ it's to be opened to traffic.
Not until ________did he leave.
I _________ in the countryside, but these days I________ in the city.