Explanation:

The correct answer is option 'C' - oil in pickles stops the action of micro-organisms. Let's understand why this is the correct answer.

1. Introduction to the role of oil in pickles:
Oil is commonly used in pickles as a preservative. It helps to extend the shelf life of pickles by preventing the growth of micro-organisms that can spoil the food. Pickles are generally made by fermenting vegetables or fruits in a brine solution, which creates an acidic environment. While the brine solution itself helps in preserving the pickles, the addition of oil provides an extra layer of protection.

2. How oil stops the action of micro-organisms:
When oil is added to pickles, it forms a layer on the surface that acts as a barrier. This barrier prevents the entry of air and moisture, which are essential for the growth and survival of micro-organisms. Without access to these necessary resources, the micro-organisms are unable to multiply and carry out their metabolic activities, thereby stopping their action.

3. Oil and the preservation of pickles:
In addition to creating a physical barrier, the oil in pickles also has antimicrobial properties. It contains compounds that have the ability to inhibit the growth of various micro-organisms, such as bacteria, yeast, and molds. These antimicrobial properties further contribute to the preservation of pickles by preventing the spoilage caused by these micro-organisms.

4. Other roles of oil in pickles:
Apart from its antimicrobial effects, oil also adds flavor and texture to pickles. It helps to enhance the taste and mouthfeel of the pickles, making them more enjoyable to consume. Additionally, oil can act as a preservative by preventing the oxidation of certain components in the pickles, such as vitamins and pigments. This helps to maintain the nutritional value and visual appeal of the pickles.

5. Conclusion:
In conclusion, oil in pickles stops the action of micro-organisms by creating a physical barrier and having antimicrobial properties. It helps to preserve the pickles by preventing spoilage and maintaining their quality.

C