(44. SUBSTANCE) ______
The phrase "keeps sellers on their toes" in the passage mostly means "______".
The examination was not very difficult, but it was_____________________ long.
Regular exercise and good diet will bring______fitness and health.
_______ has been a topic of continual geological research.
It is stated in the passage that____________________ .
The pool should not be made so deep______small children can be safe there.
__________ John Kennedy was elected president, he was the youngest American President ever.
The Lake District,____________________ was made a national park in 1951, attracts a large number of tourists every year.
Stephanie: "Oh, no! I left my book at home. Can I share yours?" Scott: "______ "
We must push the piano to the corner of the hall to_____________________ our party tonight.