Answer the following question given this paragraph: 

Some springs have water that contains minerals. Groundwater dissolves minerals out of the rock as it seeps through the pores. The water in some springs is hot because it is heated by hot magma. Many hot springs are also mineral springs. That’s because hot water can dissolve more minerals than cold water.


Q: The water in some springs are hot because they're heated by what?

 Choices:

- gravity

- the sun

- fires

- hot magma

A:
hot magma
