Question

What is the force that can cause two pieces of iron to attract each other?

Answer 1

Is it A ?  Yes !  Two pieces of iron DO always attract each other with equal and opposite gravitational forces, although the forces are so small that we never notice them.

Is it B ?  Yes, it could be.  If at least one of the pieces of iron is magnetized, then they can attract each other with equal and opposite magnetic forces.

Is it C ?  Yes, it could be.  But the pieces of iron would have to be joined by a stretched rubber band.  Then they would attract each other with equal and opposite elastic forces.

Is it D ?  Yes, it could be.  If one of the pieces of iron carries a net electric charge, then they attract each other with equal and opposite electrostatic forces.  

Answer 2

Answer:

B. Magnetic Force

Explanation:

two pieces of irons cannot attract each other unless at least one of them is magnetize. That force is called magnetism.