I am inclined to say 1. core and mantle... but im not entirely sure...
sorry not much help at all!
Answer:
a series of pools built like steps to enable fish to bypass a dam or waterfall.
Explanation:
A fish ladder, also known as a fishway, fish pass or fish steps, is a structure on or around artificial and natural barriers to facilitate diadromous fishes' natural migration.
Answer:
Roundworm
Explanation:
Unsegmented kicks out the possibility of A or D. Roundworms are pointed at their ends and have distinct males and females
