Answer the following question given this paragraph: 

Figure below shows a diagram of Mercury’s interior. Mercury is one of the densest planets. Scientists think that the interior contains a large core made mostly of melted iron. Mercury's core takes up about 42% of the planet's volume. Mercury's highly cratered surface is evidence that Mercury is not geologically active.


Q: What do scientist's believe mercury's core is mostly made of?

 Choices:

- water

- quicksilver

- helium gas

- melted iron

A:
melted iron
