The picture below shows three objects made of iron.

Each pure element has certain chemical properties, a specific atomic arrangement and a specific crystalline structure that distinguish this pure element from other elements.

On the other hand, the mass of any substance/object depends on the AMOUNT or the QUANTITY of matter in the object.

Based on the above, three objects made of pure iron would have:
Different masses
Same arrangement of atoms
Same crystal structure
Same chemical properties

Comparing the above to the given choices, we would find that the best choice is:
b. They have the same chemical properties

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