Why is the passage an example of a secondary source? The author is describing a firsthand account of the ruins of Pompeii.
The author is providing commentary on his discovery in the ruins of Pompeii.
The author is explaining what he experienced during the eruption of Mount Vesuvius.
The author is presenting evidence about the damage caused by the eruption of Mount Vesuvius.

the correct answer is - they each vary in size and temperature.

the layers of the earth are not monotone, they are all different, have different sizes and properties.

the four layers are the outer crust, the mantle, the outer core, and the inner core.

the outer crust is solid. it is the top layer, the one we live on, and it is also the smallest and coldest one.

the mantle is lying right bellow the outer crust. it is much bigger, and much hotter, and it is also the layer that influences heavily the upper crust layer with its convection currents.

the outer core is liquid, very hot, relatively big, and it is the third layer (top to bottom).

the inner core is the hottest layers, it is occupying the central part of the planet, and it is the basis on top of all other layers lie on.