Match the gases in column A with their harmful effects in column B: (i) Carbon monoxide (ii) Oxides of nitrogen (iii) Carbon dioxide, matched with (a) causes acid rain (b) causes global warming (c) forms carboxy-haemoglobin.
Carbon monoxide binds with haemoglobin to form carboxy-haemoglobin, oxides of nitrogen contribute to acid rain, and carbon dioxide is a major greenhouse gas causing global warming, matching (i)-(c), (ii)-(a), (iii)-(b).
Re-check your working by substituting the answer back into the original question.