11. It's interesting _________ Phong Nha cave. * A.visit B.to visit C.visiting D.visited 12. They are certain_________ they will pass the exam easily. * A.which B.what C.where D.that 13. Drink cans are brought back to the factory for _________ . * A.recycling B.buying C.making D.eating 14. Cloth bags _________ instead of plastic bags. * A.are used B.used C.is used D.use 15. I promise that I _______ for school. * A.am not late B.don't be late C.will be late D.won't be late 16. I ___________ you as soon as I finish the chores. * A.call B.will call C.called D.calling 17. I will go to university ____________continue my studies * A.in order not to B.so that C.not to D.in order to 19.He is delighted that you are ___________in protecting environment. * A.uninterested B.interesting C.interested D.interest