Ducks developed webbed feet to help them swim better .
(Ducks; developed; webbed feet; to help them swim better) Context(Ducks developed,List([0, 15))):(Ducks; developed webbed feet to help; them swim better) Context(Ducks developed to help,List([0, 35))):(them; swim better; )
Ducks developed,List([0, 15)) Ducks developed to help,List([0, 35))
Ducks Ducks them
developed developed webbed feet to help swim better
webbed feet to help them swim better
them swim better