In the past several years, we have become more aware of ---- conditions in the environment. Scientists have recently reported that ozone has declined-----. They noted that a hole in the ozone layer over Antartica----.Besides, they blamed the widespread ----of certain chemicals for the ozone decrease. Scientists have warned----- about the greenhouse effect, the gradual warning of the Earth because heat from the sun 's ray is prevented from radiating back into space by a blanket of artifical gases. The chief gas in the greenhouse effect--- carbon dioxide. Moreover, waste disposal has become a significant -----. That means we not only have tons and tons of household garbage to get rid of, but we also have hazardous waste from nuclear facilities and plants. All of these problems are -----, because they must be solved ------ quickly. Awareness is good, but that is not good enough, so everyone must ----- right now.