A rigid outer layer comprising the upper mantle and crust.

A rigid outer layer comprising the upper mantle and crust.

• A. Lithosphere
• B. Atmosphere
• C. Biosphere
• D. Hydrosphere

Answer: (A)

The concept being tested is identifying Earth’s rigid outer shell that comprises the crust and the upper part of the mantle. This rigid shell, known as the lithosphere, forms the brittle, outer layer that makes up the tectonic plates. It includes both continental and oceanic crust plus the upper mantle and behaves as a solid shell floating on the more ductile layer beneath it. That’s why the term lithosphere is used to describe this outermost, rigid portion of the planet. The other options refer to different Earth systems: the atmosphere is the gaseous envelope surrounding Earth, the biosphere encompasses all living organisms and their environments, and the hydrosphere covers all water on Earth. None of these constitute the rigid outer shell that includes the crust and upper mantle.

The concept being tested is identifying Earth’s rigid outer shell that comprises the crust and the upper part of the mantle. This rigid shell, known as the lithosphere, forms the brittle, outer layer that makes up the tectonic plates. It includes both continental and oceanic crust plus the upper mantle and behaves as a solid shell floating on the more ductile layer beneath it. That’s why the term lithosphere is used to describe this outermost, rigid portion of the planet.

The other options refer to different Earth systems: the atmosphere is the gaseous envelope surrounding Earth, the biosphere encompasses all living organisms and their environments, and the hydrosphere covers all water on Earth. None of these constitute the rigid outer shell that includes the crust and upper mantle.