Assertion: porcupine's quill | /r/CapableOf | penetrate the surface
Facets:
value: easily
type: MANNER
value: because of their hook shape
type: CAUSE
Source sentences:
text: A group of scientists studied this phenomenon and found that the tip of each quill has a tiny rear-facing spike, meaning that the quills easily penetrate the surface but are hard to remove because of their hook shape.