Acid rain leads to fish mortality. Many
species of fish cannot survive in aquatic environments where the pH is below
5.0. If the water is too acid, the gill systems of many kinds of fish can be
damaged. (21) , the acid alters the blood chemistry of all
fish. As a result, the fish population in an acidic environment decreases
(22) becomes extinct. Approximately 20 percent of the lakes in Scandinavia are without fish. Moreover, in Nova Scotia the (23) salmon industry may be threatene A. piece B. portion C. section D. segment 更多"Directions: There are 15 questions "的相关试题: [单项选择] Directions: There are 15 questions in this part of the test. Read the passage through. Then, go back and choose one suitable word or phrase marked A, B, C or D for each blank in the passage. Mark the corresponding letter of the word or phrase you have chosen with a single bar across the square brackets on your Machine-scoring Answer Sheet.
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