It worries the couple a lot ______ their only son is behaving worse and worse these days.
15. The factory _______ large numbers of tractors to the peasants.
14. The teacher insisted _______ until we finished the work.
13. — How do you keep fit?— By having a healthy diet and _________ regularly.
12. Having finished their morning work, the clerks stood up behind their desks, ________ themselves.
11. ________ no need for us to discuss the problem again. It has already been settled.