Assertion: sea otter's rock | /r/HasProperty | unique
Facets:
value: to each otter
type: OTHER
Source sentences:
text: Each otter’s rock is unique and is kept until it breaks.
text: They have a “pouch” under their forelegs that goes across the chest, here they store food they collect to bring to the surface and eat, as well as, a rock that is unique to each otter.