There used to be a small school,___________?
The research is so designed that once________nothing can be done to change it.
Visitors________not to touch the exhibits.
It is known to all that________you exercise regularly, you won't keep good health.
—What would you do if it________tomorrow?—We have to carry it on, since we've got everything ready.
We all know how difficult it is for all of us to eat better, exercise more, and sleep enough________we know we should.