Anchor: For example, nitrates account for 20-40 percent of visibility impairment in national parks and wilderness areas in Southern California.
Entailed: The parks and wilderness of Southern California have nitrates count for about 20-40 percent of visibility impairment.
Contradiction: There is no visibility impairment in the wilderness areas of Southern California. 
Contradiction: The boy has no head.
Contradiction: A human skinning
Contradiction: Two people sat far away from the siren.
Contradiction: Students have been able to ask for written evaluations.