Answer:
C
Explanation:
Bauxite is the most common aluminum ore. Approximately 98% of primary aluminum production is based on bauxite. In the former Soviet Union, aluinite and kaolinite are also used in small proportions for aluminum production. Bauxite is a naturally occurring, heterogeneous material composed primarily of one or more aluminum hydroxide minerals plus various mixtures of silica, iron oxide, titania, and other impurities in trace amounts. The principal aluminum hydroxide minerals found in varying proportions within bauxite are gibbsite (trihydrated) and boehmite and diaspore (both monohydrated). The content of aluminum oxide is 30–60%. Bauxite is generally extracted by open cast mining from strata, typically 4–6 m thick under a shallow covering of topsoil and vegetation (Table I).
