The correct answer to the question is C. marble. Explanation of the Correct Answer

1. Formation of Marble: Marble is a metamorphic rock that forms when limestone, which is a sedimentary rock primarily composed of calcium carbonate (CaCO₃), is subjected to high heat and pressure. This process is known as metamorphism. During metamorphism, the original limestone undergoes a transformation where the minerals recrystallize, resulting in the formation of marble. The heat and pressure cause the calcite in limestone to recrystallize into a denser and more crystalline structure, which is characteristic of marble.
2. Characteristics of Marble: Marble is known for its beautiful patterns and colors, which are a result of impurities in the original limestone. It is often used in sculpture and architecture due to its aesthetic appeal and ability to take a high polish.

Explanation of Why Other Options Are Incorrect

• A. Slate: Slate is a metamorphic rock that forms from shale, which is a sedimentary rock composed of clay minerals. The process involves low-grade metamorphism, where heat and pressure cause the clay minerals to align and form a denser rock. Since slate originates from shale and not limestone, it is not the correct answer.
• B. Graphite: Graphite is a form of carbon that can form under high pressure and temperature conditions, but it is not a metamorphic rock derived from limestone. Instead, graphite can form from the metamorphism of organic materials or as a result of high-pressure conditions in certain geological settings. Therefore, it does not relate to the transformation of limestone.
• D. Gneiss: Gneiss is another type of metamorphic rock, but it typically forms from the metamorphism of igneous rocks (like granite) or sedimentary rocks (like shale) under high temperature and pressure. Gneiss is characterized by its banded appearance due to the segregation of mineral grains. Since it does not originate from limestone, it is not the correct answer.

Summary of Key Points

• Marble is the metamorphic rock formed from limestone under heat and pressure.
• Slate originates from shale, not limestone.
• Graphite is a form of carbon and not a metamorphic rock from limestone.
• Gneiss forms from other rock types, primarily igneous or sedimentary, and not from limestone.

Revision Summary

• Marble is formed from limestone through metamorphism.
• Slate is derived from shale, not limestone.
• Graphite is not a metamorphic rock from limestone.
• Gneiss forms from other rock types, not limestone.

Understanding these concepts will help clarify the relationships between different rock types and their formation processes in geology and agricultural science contexts.