How much producer biomass is supported in the ecosystem?

Apart from bacteria, the total global live biomass has been estimated as 550 or 560 billion tonnes C, most of which is found in forests. Shallow aquatic environments, such as wetlands, estuaries and coral reefs, can be as productive as forests, generating similar amounts of new biomass each year on a given area.

main function of the circulatory system in multicellular organisms is to circulate blood and oxygen in our body .so the right option is
A) to bring oxygen into the lung 
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