Only with the discovery of an ozone hole over Antarctica in 1985 did chemical companies finally relinquish their opposition to a ban on chlorofluorocarbons (CFCs), which destroy ozone. The discovery suggested that strong political action to halt production of CFCs might be (i)_____, and fortunately, the chemical industry no longer felt compelled to oppose such action: although companies had recently (ii)_____ their research into CFC substitutes, studies they had initiated years earlier had produced (iii)_____ results.
答案：A,F,G