Zinc displaces copper from its solution because:

Explanation

Option D is correct because zinc's smaller reduction potential (-0.76V) compared to copper's (+0.34V) signifies that zinc is more reactive. In electrochemical terms, a metal with a lower reduction potential can displace a metal with a higher reduction potential from its compound in solution. Therefore, zinc can easily displace copper from its solution. Option A is incorrect because the atomic number does not dictate the reactivity of metals. Option B misstates the relationship between the reduction potentials, as zinc's is lower than that of copper. Option C, while potentially true in some contexts, does not pertain to the displacement reaction, as reactivity is the determining factor.