Which of the following could be classified as a substance that has the physical property of magnetism?

Of the following given choices;

A. iron

B. plastic

C. aluminum

D. wood

The answer is; A

Magnetism is the result from the unpaired spins of electrons in the orbital shells of the atoms of an element. Aluminum (though a metal with +3 valency like iron) has it S and P orbitals filled hence most of its electrons are paired. Iron, on the other hand, a transitional metal, has a D orbital that can be filled before the P orbital is filled. Therefore, there is a higher net unpaired spin of electrons giving the atoms net magnetic properties.  

the answer would be a