1) Global warming ___is believed__ (to believe) to be caused by the greenhouse effect. 2) The seas_are filled) with poison: industrial and nuclear waste, chemical fertilisers and pesticides. 3) If nothing (is done) about it, one day no animal or plant will be able to live in the seas. 4) Tons of harmful substances(are emitted daily) by industrial enterprises. 5) As globalization continues and the earth’s natural processes transform local problems into international issues, few societiesare left) untouched by major environmental problems. 6) Acid rain, one of the most important environmental problems of all, cannot be seen). The invisible gases that cause acid rain usually come from automobiles or coal-burning power plants. 7) Air pollution can have serious consequences for the health of human beings; the natural ecosystems are affected) severely by it.
