Explanation:

The continental crust is primarily composed of lighter, less dense rocks, predominantly granitic in nature. Geologically, it is often referred to as 'Sial' because its main mineral constituents are **Si**lica ($\text{SiO}_2$) and **Al**umina ($\text{Al}_2\text{O}_3$). Option (A) Silica and iron are not the primary constituents of the continental crust; iron is more prevalent in the Earth's core. Option (B) Magnesium and Nickel are incorrect; magnesium is a significant component of the oceanic crust (Sima), and nickel is primarily found in the core. Option (C) Iron and Nickel (Nife) are the main constituents of the Earth's core, not the crust. Therefore, Silica and alumina accurately describe the main mineral composition of continental masses.