Among the given options, option 3, Graphite, is an element.
An element is a substance that cannot be broken down into simpler substances by chemical means. It consists of only one type of atom, which is the basic building block of matter.
Option 1, Alumina, is not an element. Alumina is a compound made up of aluminum and oxygen atoms.
Option 2, Brass, is also not an element. Brass is an alloy, which is a mixture of copper and zinc.
Option 4, Silica, is not an element either. Silica is a compound made up of silicon and oxygen atoms.
Therefore, the correct answer is option 3, Graphite, which is an element as it is composed of only carbon atoms.