WHAT DOES THE PASSAGE MAINLY DISCUSS

40. What does the passage mainly discuss? A. The time required for species to adapt to new environments B. The cause of the extinction of the dinosaurs C. The variety of species found in tropical rain forests D. The impact of human activities on Earth's ecosystems Mark the letter A, B, C, or D on your answer sheet to indicate the sentence that best joins each of the following pairs of sentences in each of the following questions