The pollution problem caused by the burial of industrial waste is most prominent in the moderately developed countries, while it is not prominent in the developed and underdeveloped countries. Underdeveloped countries are because there is not much industrial waste that can be processed. Developed countries are either because they have effectively reduced industrial waste, or because they have effectively processed industrial waste. Country H is a moderately developed country. Therefore, the pollution caused by the burial of industrial waste will be substantially changed in five years.
The statement 'Country H will maintain its development level unchanged for five years' is most likely to be assumed by the above argument.