( Snakes ( ( ( use ( their tongues ) ) ( to smell ) ) . ) )
(ROOT (S (NP (NNS Snakes)) (VP (VBP use) (NP (PRP$ their) (NNS tongues)) (PP (TO to) (NP (NN smell)))) (. .)))
Snakes use their tongues to smell.
(ROOT (S (NP (NNS Snakes)) (VP (VBP use) (NP (PRP$ their) (NN tongue)) (PP (TO to) (NP (NN smell) (NNS things)))) (. .)))
Snakes use their tongue to smell things.