I planned ________ to see you last week, but I was ill.
We often think of the days ___we spent together on the island.
Air, _ __we breathe every day, is around us all the time.
The radio set __ _ last week has been out of order.
He is a man of great knowledge, ___much can be learned.
Now we can fly to Tokyo. There was a time ________ we had to take a boat.