All of the following had a role in europe develop into the modern grouping of nation-states we see today except: a) conflict b) religion c) martial alliances d) feudialism

Which one is the underlined word?

Air pollution: “combustion results in gases such as nitrogen oxides, nitrogen dioxide and particulates. the main causes of air pollution include transport, domestic combustion and industrial processes. pollutants from these sources can cause problems in the immediate vicinity and a distance away.”