Introduction:
Insectivorous plants are unique plants that have adapted to survive in nutrient-poor soils by capturing and digesting insects. These plants obtain essential nutrients, such as nitrogen, phosphorus, and sulfur, from the insects they trap. However, the soil in which these plants grow is deficient in certain nutrients, which leads to their adaptation to carnivory.

Explanation:
The correct answer is option 'C' - nitrogen. Here's an explanation of why the soil in which insectivorous plants grow is deficient in nitrogen:

Nitrogen Deficiency:
1. Nitrogen is an essential nutrient required by all plants for their growth and development. It is a key component of proteins, nucleic acids, and chlorophyll.
2. In most ecosystems, nitrogen is readily available in the soil through the decomposition of organic matter and the action of nitrogen-fixing bacteria.
3. However, in nutrient-poor soils, such as those found in bogs, marshes, and other wetlands where insectivorous plants typically grow, nitrogen availability is limited.
4. The low nitrogen content in these soils is primarily due to the slow decomposition of organic matter in waterlogged and acidic conditions.
5. Additionally, the high levels of water in these soils result in the leaching of nitrogen, further reducing its availability for plants.
6. As a result, insectivorous plants have evolved to capture and digest insects to supplement their nitrogen requirements.
7. They have specialized structures, such as pitcher traps, sticky leaves, or snap traps, that enable them to capture and digest insects.
8. The insects provide a rich source of nitrogen that is otherwise lacking in the soil, allowing the plants to thrive in these nutrient-poor environments.

Conclusion:
In conclusion, the soil in which insectivorous plants grow is deficient in nitrogen. These plants have adapted to carnivory as a means to supplement their nitrogen requirements by capturing and digesting insects. This adaptation allows them to thrive in nutrient-poor environments such as bogs and marshes.

Nitrogen..!!!