Never before _______ seen anybody who can play tennis as well as Robert.
—At last I’ve made it.I am on top of the world. —______
We congratulated him ______ his getting a gold medal.That is to say: we offered him our congratulations ______ his getting a gold medal.
You have made a few mistakes in your composition but ______ you have done well.
In the experiment you should keep a watchful eye ______ the developments and record every detail.
He said ______ couldn’t he work out the problem but his teacher didn’t know how to do it.