The correct answer is A. Alumina.
Alumina is an element with the chemical symbol Al2O3. It is a white, odorless, tasteless solid that is the most abundant aluminum compound in the Earth’s crust. Alumina is a major component of bauxite, the ore from which aluminum is extracted. It is also used in a variety of other products, including ceramics, abrasives, and refractories.
Brass is an alloy of copper and zinc. It is a yellow, reddish-brown, or golden-colored metal that is used in a variety of products, including jewelry, musical instruments, and plumbing fixtures.
Graphite is a form of carbon that is made up of carbon atoms arranged in a hexagonal lattice. It is a soft, black, and slippery solid that is used in a variety of products, including pencils, lubricants, and electrodes.
Silica is a compound of silicon and oxygen with the chemical formula SiO2. It is a hard, white, or colorless solid that is found in sand, quartz, and other minerals. Silica is used in a variety of products, including glass, ceramics, and semiconductors.
In conclusion, the correct answer is A. Alumina. Alumina is an element, while brass, graphite, and silica are all compounds.