Answer:
Z: Gamma rays
X: Visible light
Step-by-step explanation:
A close look at the diagram attach shows the core of the sun and then the external surface.
Gamma rays are intricately associated with the nuclear reactions that go on in the core of the sun that makes it to produce light. Hence Z must refer to gamma rays emitted in these nuclear processes at the core of the sun.
Visible light is given out by the sun and seen externally. Hence X is visible light.