Only Two Entries Change

This DSU forest has no path compression yet. The arrow on each node points to its parent, and parent[0] = 0.

Parent forest with root 0, node 7 four levels down 0 124 356 7

Now one call runs:

int find_set(int v) {
    if (v == parent[v])
        return v;
    return parent[v] = find_set(parent[v]);
}

find_set(7);

After it returns, how many entries of the parent array hold a different value than before?

A

7

B

2

C

3

D

1