The correct option is A CH4 and H2O
One of the important features of catalyst is the selectivity.
It is the ability of a catalyst to direct a reaction to yield a particular product selectively.
Under same reaction conditions, different products are possible for different catalyst.
Here, on reaction of CO and H2 in presence of Nickel bed, it forms CH4 and H2O products selectively.
Different products are obtained from the same reactant by changing the metal bed( catalyst).
For the same reactants, copper (Cu) metal bed forms formaldehyde and ZnO metal bed forms CH3OH.