Step 1: Nature of the reaction.
Zinc in water acts as a reducing system providing nascent hydrogen, which dehalogenates haloforms.
Step 2: Apply to chloroform.
CHCl$_3$ undergoes stepwise replacement of Cl by H under reducing conditions, ultimately forming CH$_4$.
Step 3: Conclusion.
Therefore, chloroform reduces to methane \(\Rightarrow\) (D).