Suppose Sn = X1 + + Xn is simple symmetric random walk in one dimension. Let Fn denote the information in X1, X2, . . . , Xn. For each of the following say if the process is a martingale, submartingale, or supermartingale (it can be more than one and it might be none of these) with respect to Fn. Give reasons.

2. Mn = S2 3. Mn = $3 n 4. Mn = esn 5. Mn = Sn+1 - Sn.