Which of the following statement is correct related to branch and bound method?

Why this is correct:
Branch-and-bound is an algorithmic framework for solving combinatorial optimization problems: it systematically explores a tree of subproblems (branching) and computes bounds for subproblems to prune those that cannot contain better solutions (bounding). This description (breaking into subproblems + using bounding functions) matches option 4. Why the others are wrong: 1.      “Best immediate output” is vague and misleading — branch-and-bound searches for optimal global solutions, not an “immediate” local best. 2.      It is not pure brute force to find all solutions; it prunes parts of the search space using bounds to avoid exhaustive search. 3.      While branch-and-bound can be used for constraint satisfaction problems, option 3 is incomplete/overly narrow — the method is broadly an optimization/search technique, not limited to CSPs.