Simple is the opposite of Subtle. Subtle is the opposite of Obvious. Obvious is a synonym of Evident. Evidence is derived from Evident. 
Answer is related to Test. Test is related to Experimental. Experimental is related to Theory. Theory is related to Theological. 
Simple <--Antonym--> Subtle <--Antonym--> Obvious <--Synonym--> Evident <--DerivedFrom-- Evidence 
Answer <--RelatedTo--> Test <--RelatedTo--> Experimental <--RelatedTo--> Theory <--RelatedTo--> Theological 