Runtime Environment

Consider the following statements. $S_1$: The sequence of procedure calls corresponds to a preorder traversal of the activation tree. $S_2$: The sequence of procedure returns corresponds to a postorder traversal of the activation tree. Which one of the following options is correct?

What will be the output of the following pseudo-code when parameters are passed by reference and dynamic scoping is assumed?

a=3;
void n(x) {x = x * a; print(x);}
void m(y) {a = 1; a = y - a; n(a); print(a);}
void main() {m(a);}