C

Step 1: Let's denote the resistivity of the alloy as \( \rho_{alloy} \) and the resistivity of the constituent metals as \( \rho_{metal} \).
Step 2: Generally, the resistivity of an alloy is affected by the properties of its constituent metals, but there isn't a straightforward linear relationship.
Step 3: While in certain cases, such as mixtures of metals, the resistivity can be less than or greater than that of the individual metal components, the complexity of this relationship means that there is generally no simple relation.
Therefore, option C is the most appropriate answer.