Selection is a synonym of Option. Option is related to Opportunity. Opportunity is related to Available. Available is similar to Accessible. 
Cast is a type of Gathering. Cast entails/necessarily involves Film. Film is related to Firm. 
Selection <--Synonym--> Option <--RelatedTo--> Opportunity <--RelatedTo--> Available <--SimilarTo--> Accessible 
Gathering <--IsA-- Cast --Entails--> Film <--RelatedTo--> Firm 