Chemically active fluids are . a. fluids that readily change to gases at surface conditions more basic than regular b. fluids more acidic than regular fluids c. fluids that contain large quantities of oxygen which reacts with most minerals to form new minerals during metamorphism

Option (C)

Explanation:

Chemically active fluids are defined as those liquid that are present within the  pore spaces in rocks, and are mixed up with various ions forming a definite solution. These liquids are comprised of O₂, and this directly reacts with the comprising rock minerals, due to the changing heat and pressure condition, and that results in the alteration of the present rock into a new grade of metamorphic rocks. This directly enhances the process of metamorphism, and this process is known as the metasomatism where the rock alters due to the presence of hydrothermal fluids.

Thus, the correct answer is option (C).