Electric trains have now ______ steam ones in most countries in the world.
She may have missed the train, ______ she won’t arrive for another hour.
There are more opportunities for disabled people to make______ contribution to______ society.
---What’s wrong with my stomach? ---There is nothing serious; you can __________.
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.