______ is known to all is that the old scientist, for ______ life was hard in the past, still works very hard in his eighties.
Everyone was silent as the organizer ________ the result of the speech competition.
After a few courses on painting, Helen said she would ________ oil painting in her spare time.
Most people are familiar with the idea that all matter in the universe ________ atoms.
________, Nathan gave back the enormous amount of money he found.
________ entered the classroom ________ the bell rang.