WHAT WILL THE SPEAKER PROBABLY DISCUSS NEXT

21. What will the speaker probably discuss next?A. The make-up of the ozone layer.B. The sun as a cause of ozone layer depletion.C. How to make air conditioners with fluorocarbons.D. Harmful effects of ultraviolet light.Mark the letter A, B, C or D on your answer sheet to indicate the sentence that best combines each pair ofsentences in the following questions.