Happiness is a butterfly, which, when pursued, is always just beyond your grasp, but ________, if you will sit down quietly, may alight upon you.
If we ____ now to protect the environment, we will live to regret it.
You can’t imagine the trouble we had ____ in touch with him.
____ this car with that one, he chose the latter.
He claims to _____ a round black creature moving quickly through the water.
She ____ have left school, for her bike is still here.