The right answer is B) through fall.
Nature is decidedly well done, and fall leaves in autumn is the perfect illustration! Although most trees lose their leaves in autumn, it is certainly not by caprice but by necessity. On the one hand, the mechanism of the fall of the leaves is vital for the tree which thus implements a measure of natural protection against the great colds to come. On the other hand, fallen leaves will be used by insects and microorganisms to feed on them and transform them into inorganic matter.