What makes a problem recursive?

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Group of answer choices

The solution can be found by combining the initial problem two or more times.

The solutions to the smaller pieces can be combined to find the solution to the larger problem.

The solution to the problem is always O$($ln n$).$

The solution to the problem always involves some kind of array.

The problem can be cut up into two or more pieces such that the smaller pieces are themselves instances of the problem.

The efficient solution to the problem will always be O$($k$)$ where for each k$,0<$ k $<$ n$*$n$*$n

The solution can be found using a loop.