Into which layer of the earth do plate boundaries extend?
a. outer core

b. lithosphere

c. lower mantle

d. asthenosphere

The correct answer is B. Plate boundaries extend into the lithosphere.

Explanation:

A tectonic plate or lithospheric plate is a fragment of the lithosphere which results from its cutting in the manner of a puzzle by a system of faults, ridges, rifts and subduction trenches. The lithospheric plates move a few centimeters a year in different directions, resulting in the formation of areas of divergence, subduction, collision and sliding.

Plate tectonics is the theory that explains the structure and dynamics of the Earth's surface. It states that the lithosphere, the coldest, stiffest upper portion of the Earth, is fragmented into a series of plates moving over the Earth's mantle. This theory also describes the movement of the plates, their directions and interactions. The Earth's lithosphere is divided into 7 large plates and several smaller plates or microplates. At the edges of the plates seismic, volcanic and tectonic activity are concentrated. This results in the formation of large chains and basins.

a is the answer i believe.