Answer: (iv) Answering probabilistic query — (i) Solving queries is also acceptable but (iv) is more precise.

Explanation:

Bayes Rule: $P(H|E) = \frac{P(E|H)P(H)}{P(E)}$

Uses:

• Answering probabilistic queries — compute posterior $P(query | evidence)$, e.g., $P(disease|symptoms)$.
• Solving queries in Bayesian networks: Inference via enumeration, variable elimination, MCMC.
• Classification (Naive Bayes): $P(y|x) \propto P(x|y)P(y)$
• Updating beliefs with evidence, spam filtering, medical diagnosis.

It does NOT increase/decrease complexity inherently; it enables probabilistic reasoning.

Hence (iv) Answering probabilistic query is textbook best. (i) Solving queries is vague but related — if single choice forced, pick (iv).