Identify the correct statement

$(a)\;\text{Plants and seawater are receptors of }CO_2\\(b)\;\text{Micro organisms acts as sink for dead plants and animals}\\(c)\;\text{Micro isocyanate and DDT are contaminants}\\(d)\;Pb,Hg,CO_2\;SO_2\;\text{are pollutants}$

Toolbox:
• Plants and seawater are receptors of $CO_2$
• Micro organisms acts as both sink and source for dead plants and animals
• Micro isocyanate is a pesticide and DDT is a contaminant.
• $CO_2$ is not a pollutant. $CO_2$ is a gas that has played an enormous role in the development and sustainability of all life on this Earth.
Hence (a) is the correct answer.
edited Apr 3, 2014