The core concept here is the understanding that the value of a species in an ecosystem is not solely based on its economic benefits to humans. The correct answer, B, states that all species have a right to exist, which aligns with the idea that a species' value is not solely economic. Option A is incorrect because it contradicts the premise by stating that economic value is the only measure. Option C is too narrow, as it only considers direct economic benefits. Option D is incorrect because it bases the conservation of a species on public popularity rather than its actual ecological role.