How to identify which species will undergo Oxidation and which will go Reduction
You have to look at the possible oxidation states of the atoms involved.
For instance, if you were given the molecule $\ce{F2}$, you should consider that fluorine has two possible oxidation states: 0 (in the $\ce{F2}$ molecule) and -1.
Hence, $\ce{F2}$ can only undergo reduction.
For the other molecules, you should use the same strategy: try yourself!