Correct Option: B. 40% - 60% Explanation of the Correct Answer In an incubator, maintaining the right relative humidity is crucial for the successful hatching of eggs, particularly in poultry farming. The relative humidity refers to the amount of moisture in the air compared to the maximum amount of moisture the air can hold at a given temperature.

1. Importance of Humidity in Incubation:
2. Egg Development: Eggs need a specific level of humidity to ensure proper development of the embryo. Too little humidity can lead to excessive moisture loss from the egg, causing the embryo to dehydrate and die. Conversely, too much humidity can prevent the egg from losing enough moisture, leading to issues such as poor air cell development and difficulty in hatching.
3. Optimal Range: The optimal relative humidity for incubating eggs is generally between 40% and 60%. This range allows for adequate moisture retention while still enabling the embryo to develop properly.
4. Physiological Processes:
5. During incubation, the embryo requires oxygen and releases carbon dioxide. The humidity level affects the gas exchange process through the eggshell. If the humidity is too low, the egg may lose too much water, leading to a condition known as "shrink-wrapping," where the embryo sticks to the shell and cannot hatch properly.
6. Temperature and Humidity Relationship:
7. The relationship between temperature and humidity is also important. As temperature increases, the air can hold more moisture. Therefore, maintaining a balance is essential to ensure that the eggs do not dry out or become overly saturated.

Why Other Options Are Incorrect

• Option A: 10% - 30%:
• This range is too low for incubating eggs. At such low humidity levels, eggs would lose moisture rapidly, leading to dehydration of the embryo. This can result in poor hatch rates and weak chicks.
• Option C: 70% - 80%:
• While this range might seem beneficial for maintaining moisture, it is too high for the incubation of most eggs. High humidity can lead to problems such as poor air cell development and increased risk of bacterial growth, which can compromise the health of the embryo.
• Option D: 90% - 100%:
• This range is excessively high and can create a saturated environment. Such conditions can lead to mold growth and other pathogens, which can be detrimental to the eggs. Additionally, it can prevent the eggs from losing the necessary moisture, leading to hatching difficulties.

Summary of Key Points

• The optimal relative humidity for incubating eggs is 40% - 60%.
• Proper humidity levels are crucial for embryo development and successful hatching.
• Low humidity can cause dehydration, while high humidity can lead to mold and hatching difficulties.
• Maintaining the right balance of humidity and temperature is essential for successful incubation.

By understanding these principles, students can better appreciate the importance of environmental conditions in agricultural practices, particularly in poultry farming.