**Organic Acids**

Organic acids are a class of compounds that contain the carboxyl functional group (-COOH). These acids are derived from living organisms and are typically found in natural sources such as fruits, vegetables, and other organic materials. They play essential roles in various biological processes and have a wide range of applications in industries such as food, pharmaceuticals, and agriculture.

**Explanation of the Correct Answer**

The correct answer is option 'C' - Lactic acid. Lactic acid is an organic acid that occurs naturally in many foods, especially fermented products. It is produced during anaerobic respiration in muscle cells and is responsible for the muscle fatigue and soreness experienced after intense exercise.

**Explanation of the Incorrect Options**

a) Hydrochloric acid: Hydrochloric acid (HCl) is an inorganic acid. It is a strong acid that is commonly used in laboratories and industries. Hydrochloric acid does not contain the carboxyl functional group (-COOH) and is not derived from organic sources.

b) Sulphuric acid: Sulphuric acid (H2SO4) is also an inorganic acid. It is widely used in various industries, including the production of fertilizers, dyes, and detergents. Like hydrochloric acid, sulphuric acid does not contain the carboxyl functional group and is not derived from organic sources.

d) Nitric acid: Nitric acid (HNO3) is an inorganic acid that is commonly used in the production of fertilizers, explosives, and various other chemicals. It does not contain the carboxyl functional group and is not derived from organic sources.

**Conclusion**

Lactic acid is an organic acid that is derived from living organisms and is found in natural sources. It contains the carboxyl functional group (-COOH), which is characteristic of organic acids. The other options, hydrochloric acid, sulphuric acid, and nitric acid, are inorganic acids and do not possess the carboxyl functional group.

Lactic acid is an organic acid as it is found in milk and milk products...