According to the text, what is a direct result of the asthenosphere being more pliable than the lithosphere?

The correct answer is A. The text explicitly states that the 'plastic quality of the asthenosphere is crucial' because 'It provides a movable surface upon which the more rigid lithospheric plates can drift.' This directly links the pliability of the asthenosphere to the movement of the plates.

B is incorrect because the text states that the lithosphere · is · fragmented into plates, but it does not claim that the pliability of the asthenosphere is the · cause · of this fragmentation.

C is incorrect because the text describes the asthenosphere as being 'hotter' and 'denser' as inherent properties, not as a result of its pliability. This choice reverses the cause-and-effect relationship.

D is incorrect because the text identifies the · lithosphere · , not the asthenosphere, as the layer that combines with the crust to form the 'rigid shell.' This choice confuses the two layers described in the passage.