Explanation: The rusting of iron is an example of oxidation. When iron reacts with oxygen and moisture from the air, it forms hydrated ferric oxide (Fe₂O₃·xH₂O), commonly known as rust. This process involves the loss of electrons by iron, which is a characteristic feature of oxidation.

Explanation: The pyloric sphincter is a circular band of smooth muscle located at the junction of the stomach and the duodenum (first part of the small intestine). It regulates the passage of partially digested food (chyme) from the stomach into the small intestine and prevents backflow. The cardiac sphincter, by contrast, controls food entry into the stomach from the esophagus.

In organic farming, chemical fertilizers are not used. Instead, farmers rely on natural manures, compost, and biofertilizers to enrich the soil. Organic farming avoids synthetic pesticides and focuses on maintaining ecological balance, soil fertility, and sustainable crop production.

• Intercropping: Often used to increase productivity naturally.
• Manures: Essential in organic farming for soil health.
• Biofertilizers: Widely used to promote natural nutrient availability.

Bioremediation is the process by which living organisms — mainly microbes, fungi, or plants — are used to remove or neutralize contaminants, pollutants, or toxins from soil, water, or air. These organisms break down harmful substances into less toxic or non-toxic forms, helping to clean up polluted environments naturally. It is an eco-friendly and cost-effective method for environmental restoration.

Other options (for context)

• Biotechnology: A broader field involving the use of living systems for industrial, agricultural, or medical purposes.
• Biodegradation: The natural breakdown of organic materials by microorganisms, but not necessarily aimed at pollution cleanup.
• Biomagnification: The accumulation of toxic substances in the food chain, opposite of pollution removal.