Concept:Both duralumin and alnico are alloys that share aluminium as a common component.
Explanation:Duralumin is mainly composed of aluminium, copper, magnesium, and manganese.
Its approximate composition is
94% Al,
4% Cu,
1% Mg, and
1% Mn.
Alnico is an alloy of iron, aluminium, nickel, and cobalt. Its name is formed from Al-Ni-Co.
Therefore, the element found in both alloys is aluminium, represented as
Al.
Answer:C. Al