Final answer:
The relationship between a question and its answer is equality with inherent disparities.
Step-by-step explanation:
The nature of the relationship between a question and its answer, according to the passage, is equality with inherent disparities. This means that while a question and its answer are considered equal, there are inherent differences or inequalities between them.
The passage mentions that a question-answer string q and a can be represented as part of a set of all strings denoted as S. The relationship between questions and answers is defined by relations Q and A, which are subsets of SxS. These relations signify that an answer a is related to a question q, allowing for the possibility of multiple answers to a question and vice versa.