Mobile oil is applied on iron shutters to ____friction.

Options

A. increase
B. decrease
C. remove
D. keep same

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks why mobile oil is applied on iron shutters. We need to identify the effect of mobile oil on friction.

2. **Identifying the Purpose of Mobile Oil**: Mobile oil is a lubricant. Its primary function is to reduce friction between surfaces that move against each other.

3. **Observing the Effect of Friction**: When iron shutters are used, especially in cold weather, they can become difficult to open and close due to increased friction. This friction can cause noise and resistance.

4. **Applying Mobile Oil**: By applying mobile oil to the iron shutters, we create a thin layer between the surfaces. This layer allows the shutters to slide more easily against each other.

5. **Conclusion**: Therefore, the application of mobile oil on iron shutters is intended to decrease friction, making it easier to open and close the shutters smoothly.

6. **Final Answer**: Mobile oil is applied on iron shutters to **decrease friction**.

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