Can please someone tell me the correct answer for questions 17 and 18? It's C programming

If the right subtree of a node x is not empty, which means that x has a successor node (a descendent node with a larger key) y, then y must be x's right child. the lowest ancestor of x whose left child is also an ancestor of x. x's parent. the left most descendent of x's right child. 1 or 4 1 or 2 In a full binary tree with the root at level 0, how many nodes are at level 4? 31 16 8 32