Trial is related to Test. Test is related to Classroom. you are likely to find Book in/at/on Classroom. Book can be used for Resource. 
Regret is related to Would. Would is related to Could. Could is etymologically related to Should. 
Trial <--RelatedTo--> Test <--RelatedTo--> Classroom <--AtLocation-- Book --UsedFor--> Resource 
Regret <--RelatedTo--> Would <--RelatedTo--> Could --EtymologicallyRelatedTo--> Should 