There were two boys in the lab, _______ did the experiment successfully.
The question is easy ______,so I don't think it's necessary to ask you for help.
He got seriously ill when he was a baby. Later he couldn't see anything at all. He was blind.
-What's happening in the new area? -New houses _______ recently over there.
What _____ pity that you couldn't be there to receive prize!
Experiments of this kind ______in both the U. S. and Europe well before the Second World War.