Grass is a type of Plant. Plant is a type of Communicate. Acknowledge is a type of Communicate. Acknowledge is a synonym of Proclaim. 
Situation is related to Case. Accident is etymologically related to Case. 
Grass --IsA--> Plant --IsA--> Communicate <--IsA-- Acknowledge <--Synonym--> Proclaim 
Situation <--RelatedTo--> Case <--EtymologicallyRelatedTo-- Accident 