In the context of transform$-$and$-$conquer, what does 'instance simplification' typically involve?

Please be aware that there will be point deductions for incorrect answers.

Employing dynamic programming to store intermediate results.

Reducing the problem to a different but related problem.

Changing the representation of the problem to make it easier to solve.

Transforming the problem into a simpler instance of the same problem.

Using a divide$-$and$-$conquer approach to break down the problem.

Applying a greedy strategy to simplify the problem.