What does the concept of recursion refer to in programming?

Recursion in programming is a technique in which a function calls itself to solve a problem. The essence of recursion lies in breaking down a complex problem into smaller, more manageable instances of the same problem. This process continues until a base case is reached, which provides a simple and direct solution.

For instance, in calculating factorial numbers, the factorial of a number ( n ) can be expressed in terms of the factorial of ( n - 1 ). This self-referential approach exemplifies how a larger problem can be solved through repeated application of the same logic on smaller subproblems.

This method is extremely useful for problems such as tree traversals, solving puzzles like the Towers of Hanoi, or implementing algorithms like binary search. Each recursive call effectively narrows down the scope until it meets a stopping condition, known as the base case, ensuring that the recursion will ultimately terminate with a solution.

In contrast, the other choices do not accurately define recursion. For instance, parallel execution of code refers to executing multiple processes simultaneously rather than the self-referential aspect of recursion. Control flow statements govern the flow of execution but do not inherently involve self-calling functions. Optimizing memory usage can be a result of some recursive implementations but