Step 1: Analyze the Nature of Oxides:
$GeO$: Germanium(II) oxide is acidic/amphoteric in nature.
$CO$: Carbon monoxide is a well-known neutral oxide (it reacts with neither acids nor bases to form salts).
$GeO_2$: Germanium(IV) oxide is distinctly acidic (and slightly amphoteric).
$CO_2$: Carbon dioxide is an acidic oxide (forms carbonic acid with water).
Step 2: Identify Neutral Oxides:
Common neutral oxides are $CO$, $NO$, and $N_2O$.
Step 3: Conclusion:
$CO$ is the neutral oxide.