which choice

What does the following recursive method do, if called from another public method, where the parameter p is reference to the tree root? private int undefined_Method(Node p) { if (p == null) return 0; if (p.left == null || p.right == null) return p.data; if (p.left != null && p.right = null) return p.data + undefined_Method(p.left) + undefined_Method(p.right); else return undefined_Method(p.left) + undefined_Method(p.right); } O a. It returns the summation of the data of all the nodes. Ob. It returns the summation of data of leaf nodes and nodes having two child nodes. O c. It returns the summation of data of the leaf nodes and nodes having only right child. O d. It returns the summation of data of the leaf nodes and nodes having only left child