Let G be an undirected graph. Consider a depth-first traversal of G, and let T be the resulting depth-first search tree. Let u be a vertex in G and let v be the first new (unvisited) vertex visited after visiting u in the traversal. Which of the following statements is always true?

A | {u,v} must be an edge in G, and u is a descendant of v in T |

B | {u,v} must be an edge in G, and v is a descendant of u in T |

C | If {u,v} is not an edge in G then u is a leaf in T |

D | If {u,v} is not an edge in G then u and v must have the same parent in T |