The answer is B.The persona in the poem tells s about the melancholy he felt and the feeling of isolation that he sensed as he walked during this season in which he sees dead leaves a lot..The journey he has completed takes place diring the end of autumn, so he feels sad probably because it is the end of certain living things in nature.At the same time he could be indicating that he is sad because a love story ended as summer ends and gives way to fall and winter in which the Earth looks desolate and deprived.