The asthenosphere is the only layer listed that is viscoelastic in nature, behaving both elastically and viscously. This layer allows for the movement of tectonic plates and deforms under stress over geological time. In contrast, the other layers mentioned do not exhibit viscoelastic properties. ;
The asthenosphere is the layer of the Earth that is viscoelastic in nature, allowing for gradual deformation and tectonic plate movement. The other options, mesosphere, stratosphere, and lithosphere, do not exhibit viscoelastic properties. Therefore, the correct answer is the asthenosphere.
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