Input (grade 12): Gastropods typically have a well-defined head with two or four sensory tentacles with eyes, and a ventral foot, which gives them their name (Greek gaster, stomach, and poda, feet).
Output (grade 6): They typically have a well-defined head with two or four sensory tentacles. They also have a ventral, which gives them their name (Greek gaster, stomach, and poda, feet).