The correct option is B Philanthropist
One who loves mankind is option B, Philanthropist. Option A, 'Anthropologist' is someone who scientifically studies humans, their beliefs, customs and relationships. Option C, 'Seismologist' is someone who studies sudden violent movements of the earth connected with earthquake. Option D, 'Optometrist' is someone who's job is examining people's eyes and selling contact lenses etc. Thus, options A, C and D are incorrect and the correct word for the given phrase is Option B, Philanthropist.