sentence2_structure: Snakes<>use<>their tongue<>to smell things$$$Snakes<>use their tongue to smell<>things
sentence1: Snakes use their forked tongues to &quot;smell&quot; or &quot;taste,&quot; constantly flicking them to pick up any air-borne particles and odors.
sentence2: Snakes use their tongue to smell things.
question: What do snakes use to smell things?