If two samples have very similar melting points, what does that indicate about them? What does it mean if they have very different melting points?

Options:

a) Similar melting points indicate identical chemical compositions and molecular structures, while different melting points suggest different chemical compositions or impurities.

b) Similar melting points imply similar chemical compositions but may have different molecular structures, while different melting points may indicate identical compositions with varying impurities.

c) Similar melting points suggest identical chemical compositions but potentially different molecular structures, while different melting points may indicate variations in both composition and structure.

d) Similar melting points indicate identical chemical compositions but potentially different molecular structures, while different melting points could be due to variations in impurities or crystalline forms.