This morning the police ______ to the scene of the crime when it began to rain.
Don't give up, Tom. You haven't realized ______ great progress you've made!
Grace has been a teacher for two years. She ______ in a school when I first met her.
Mary is tired of learning because she is always ______ to do better than she can , both at school and at home.
—All the oil in the world will ______ some day.—Yeah. What shall we use at that time?
—How wonderfully Jim is swimming in the pool!—It ______ be Jim. I am not sure.