The characteristics of two layers of earth’s crust are listed. layer a: made of iron and nickel and responsible for earth’s magnetic field layer b: made mostly of solid iron which statement is true? layer a is the crust and layer b is the mantle. layer a is the mantle and layer b is the crust. layer a is the outer core and layer b is the inner core. layer a is the inner core and layer b is the outer core.

The statement that is true is the third statement: Layer A is the outer core and Layer B is the inner core.

Option C, Layer A is the outer core and Layer B is the inner core.

Explanation:

The core of earth consists of two parts - outer core and inner core

The inner core of earth is made up of iron which exits at a high temperature equivalent to temperature of sun. The pressure at this layer is extremely high and thus the metal in this part of earth's core does not convert into liquid.  

While the outer core is made up of iron, nickel and other metals (in trace amount). As the pressure in this part of earth’s core is comparatively lower than that of inner core ,the metals exists in fluid form.

Thus, option C is correct

the answer to your question is:

c. complementary base-pairing