Put the verbs in brackets into the correct passive form. 1)

Put the verbs in brackets into the correct passive form. 1) Global warming ___is believed__ (to believe) to be caused by the greenhouse effect. 2) The seas_________(to fill) with poison: industrial and nuclear waste, chemical fertilisers and pesticides. 3) If nothing __________(do) about it, one day no animal or plant will be able to live in the seas. 4) Tons of harmful substances___________(to emit daily) by industrial enterprises. 5) As globalization continues and the earths natural processes transform local problems into international issues, few societies__________(to leave) untouched by major environmental problems. 6) Acid rain, one of the most important environmental problems of all, cannot________(to see). 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 ecosystem_________(to affect) severely by it.