Well, because the word 'mother' is the English translation of the Latin word 'mater', they mean the same thing. So, I am assuming we are supposed to find two words which have the same etymology like this one, to complete the analogy. So, I believe the answer is A) autonomy : autos, because 'autos' is the root of the word 'autonomy', the same way 'mater' is for 'mother'.