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Air pollution is a major problem all over the world today. Studies have found that the single biggest------------------(1- contributor2-provider3-cause 4-factor) to the problem is motor vehicle. -------------------(1-Although2-However3-Therefour4-Eventhough), many other man-made sources pollute our atmosphere, --------------(1-such 2-same3-similar4-example) factories power stations, building and the ------------------(1-burning 2-burnt-burn-burned)of fossil fuels. Some natural sources also ------------(1-cause2-harm3-affect4-effect) air pollution active volcanoes and forest fires (1-produce2-develpe 3-expel 4- incur) lots of pollutants. However it is the (1-expanded 2-intensified 3-added 4-broaden)duse and increased number of cars that (1-are 2-were 3-is 4-was) doing the most damage. Recent studies have (1-confirmed 2-explained3-illustrated-4-displayed) that air pollution can increase the risk(1- of 2-from3-for 4-in) dying from health problems such as heart attacks and lung cancer. Therefore it is imperative that countries invest more in green technology in order to protect the environment and minimize the negative impact of air pollution on humans.
I think the answers are below but I am not sure
1) Contributor
2) Although
3) Such
4) Burning
5) Cause
6) Produce
7) Expanded
8) Are
9) Confirmed
10) of