The correct answer is - b) the northeast.
According to this map, the least amount of Biosphere Reserves in South America has the northeastern part of the continent. This part of South America is actually dominated by the biggest tropical rainforest in the world, the ''lungs of the Earth'', the Amazon rainforest. This is the place on the surface of our planet where there's the biggest diversity in flora and fauna, and it is also the place through which flows the river with the biggest amount of water, the Amazon River.