Assertion: cactus's thorn | /r/HasProperty | placed at right angles
Facets:
value: exactly
type: DEGREE
value: for the best defense
type: PURPOSE
Source sentences:
text: But the Opuntias had yet to meet another enemy; desert animals were hungry for their rich stores of nutriment and water, so the rudimentary leaves were replaced by awful needle-like thorns placed at exactly the right angles for the best defense.