`CO_2` can be used to preserve food grains from destruction by insects.

Explanation

**Step-by-Step Text Solution:**

1. **Understanding the Role of CO2:**
- Carbon dioxide (CO2) is a colorless gas that is naturally present in the atmosphere. It is produced by the respiration of animals and plants and is also a byproduct of burning fossil fuels.

2. **Insect Infestation in Food Grains:**
- Food grains are often susceptible to damage from various insects. These insects can consume the grains, leading to significant losses in food supply.

3. **Mechanism of CO2 in Pest Control:**
- CO2 can be used as a method to preserve food grains by creating an environment that is inhospitable for insects. When the concentration of CO2 is increased, it can lead to suffocation of the insects.

4. **Effectiveness of CO2:**
- Research indicates that insects are killed more rapidly by exposure to high concentrations of CO2 compared to environments with low oxygen levels. This means that CO2 is an effective agent for pest control.

5. **Application in Food Preservation:**
- In practical applications, food grains can be stored in sealed containers where CO2 levels are increased. This method helps in preserving the grains by preventing insect infestations.

6. **Conclusion:**
- Therefore, the statement that CO2 can be used to preserve food grains from destruction by insects is true. It is an effective means of pest control that helps in maintaining the quality and quantity of food grains.

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