Fill in the blanks with proper words, then answer the following questions. scientists/ pollution/ serious/ factories exhaust/ reduce/ require/ percentage Everyone wants to reduce (1) _______. But the pollution problem is as complicated as it is (2) _______. It is complicated because much pollution is caused by things that benefit people. For example, (3) _______ from automobile caused large (4) _______ of air pollution. But the automobile provides transportation to millions of people. (5) _______ discharge much of the material that pollutes air and water, but factories give employment to a large number of people.