Consider the following statements.
- S1: The sequence of procedure calls corresponds to a preorder traversal of the activation tree.
- S2: The sequence of procedure returns corresponds to a postorder traversal of the activation tree.
Which one of the following options is correct?
S1 is true and S2 is false
S1 is false and S2 is true
S1 is true and S2 is true
S1 is false and S2 is false