M. Ananda Kumar, scientist, Nature Conservation Foundation says that elephants are "engineers of the eco-system. He explains : they are seed (1)_____ . Forests without (2)_____ have been observed to not have young (3)_____ at all. This is because (4)_____ species disperse seeds only through elephants." The animals are phenomenal at (5)_____ themselves to new ecological conditions and negotiating a problem.
Select the most appropriate option to fill in blank No.(4)