( ( This tongue-flicking ) ( ( ( is actually ) ( ( ( the manner ) ( by ( which ( ( the snake ) ( `` ( smells '' ) ) ) ) ) ) ( its surroundings ) ) ) . ) )
(ROOT (S (NP (DT This) (NN tongue-flicking)) (VP (VBZ is) (ADVP (RB actually)) (NP (NP (DT the) (NN manner)) (PP (IN by) (SBAR (WHNP (WDT which)) (S (NP (DT the) (NN snake)) (VP (`` ``) (VBZ smells) ('' ''))))) (NP (PRP$ its) (NNS surroundings)))) (. .)))
This tongue-flicking is actually the manner by which the snake &quot;smells&quot; its surroundings.
(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.