What are the set of functions that are to be executed to get the following output? cat

Question:What are the set of functions that are to be executed to get the following output? cat

1.push(c, s); push(a, s); push(t, s); pop(s); pop(s); pop(s);

2.push(c,s); pop(s); push(a,s); pop(s);push(t,s);pop(s);

3.pop(c ); pop(a); pop(t);

4.push(c,s); push(a,s); pop(t);

Answer:2