Inferring Relationships - Example 6

Here the solution is A.

It is only when you fill the gaps with "purposeful" and "unplanned" that you produce two word-pairs that stand in an analogous relationship to one another. Both word-pairs are synonyms respectively, i.e. they have the same meaning. "Purposeful" thus means the same as "intentional", and "unplanned" means the same as "coincidental". In (B), (C) and (D) there are no analogous relationships between the word-pairs.