Answer the following question given this paragraph: 

The seafloor spreading hypothesis brought all of these observations together in the early 1960s. Hot mantle material rises up at mid-ocean ridges. The hot magma erupts as lava. The lava cools to form new seafloor. Later, more lava erupts at the ridge. The new lava pushes the seafloor that is at the ridge horizontally away from ridge axis. The seafloor moves!.


Q: New seafloor forms when what object cools?

 Choices:

- ash

- debris

- rain

- lava

A:
lava
