Answer the following question given this paragraph: 

The core is the Sun's innermost layer. The core is plasma. It has a temperature of around 15 million degrees Celsius (°C). Nuclear fusion reactions create the immense temperature. In these reactions, hydrogen atoms fuse to form helium. This releases vast amounts of energy. The energy moves toward the outer layers of the Sun. Energy from the Sun's core powers most of the solar system.


Q: The innermost layer of the sun is known as what?

 Choices:

- photosphere

- surface

- convective zone

- core

A:
core
