Having an issue with this recursive drefintion.

Let w be the string created by concatenating i copies of w. For example, w = ww. Which of the following are correct recursive definitions for the set W = {w' :i e N}? D Base case: the empty string, w W. Recursive rule: w' = w 1w W. O Base case: the empty string, w e W. S ww'-1, i is odd Lecursive rule: w' I w/?w/2, i is even e W. HERIBERTAFEREESEEEEEEEEEEEEE! O Base case: the empty string, w e W. Recursive rule: w' ww- 1 e W