Stack enumeration — choose the correct code to access all elements of a System.Collections.Stack instance.

Introduction / Context:
Like Queue, Stack supports enumeration through GetEnumerator(). Understanding iteration without indexing is important for LIFO containers.

Concept / Approach:
Call st.GetEnumerator(), loop with MoveNext(), and access Current. Alternatively, foreach (var x in st) is the idiomatic approach.

Why Other Options Are Wrong:
Option A: Type mismatch (GetEnumerator returns IEnumerator). Option B: GetEnumerable() does not exist. Option D: GetEnumerator is not static. Option E: Stack is not index-based.

Final Answer:
IEnumerator e = st.GetEnumerator(); while (e.MoveNext()) Console.WriteLine(e.Current);