Answer the following question given this paragraph: 

Some volcanoes form over active hot spots . Scientists count about 50 hot spots on the Earth. Hot spots may be in the middle of a tectonic plate. Hot spots lie directly above a column of hot rock called a mantle plume . Mantle plumes continuously bring magma up from the mantle towards the crust ( Figure below ).


Q: What substance comes toward earth's crust through mantle plumes?

 Choices:

- rocks

- water

- gas

- magma

A:
magma
