Drill is a type of Teach. Help requires Teach. Help is related to Offering. 
Rib is a type of Remark. Remark is related to Observation. Observation is derived from Observer. 
Drill --IsA--> Teach <--HasPrerequisite-- Help <--RelatedTo--> Offering 
Rib --IsA--> Remark <--RelatedTo--> Observation --DerivedFrom--> Observer 