Which allotropic form of sulfur is found in the Earth's mantle and is believed to play a key role in the Earth's core-mantle sulfur cycle?
Rhombic sulfur
Monoclinic sulfur
High-pressure sulfur
Low-pressure sulfur
option C High-pressure sulfur. High-pressure sulfur is a stable form of sulfur that is found in the Earth's mantle and is believed to play a crucial role in the core-mantle sulfur cycle, which involves the transport of sulfur between the Earth's core and mantle.
Explanation of incorrect option
incorrect option A Rhombic sulfur: This is incorrect. Rhombic sulfur is an allotropic form of sulfur that exists at standard temperature and pressure, and is not found in the Earth's mantle.
incorrect option B Monoclinic sulfur: This is incorrect. Monoclinic sulfur is another allotropic form of sulfur that exists at standard temperature and pressure, and is not found in the Earth's mantle.
incorrect option D This is incorrect. There is no such known allotropic form of sulfur called "low-pressure sulfur." While sulfur can exist in different allotropic forms under different pressure and temperature conditions, the term "low-pressure sulfur" is not a recognized scientific term.