Choose from:
(a). animals;
(b). sun;
(c). humans;
(d). watershed;
(e). stars;
(f). habitat;
(g). earth;
(h). moon;
Given those answer options, answer the question: Fact 1: Planting trees has a positive impact on an ecosystem. Fact 2: Human beings live within the world's ecosystems. Given the two facts above, what does planting trees have a positive impact on?
A:
(c).