Introduction of alien species into new area poses a threat to extinction of indigenous species due to

Options

A. their high nutrient requirement
B. their symbiotic relationship
C. absence of their natural predators
D. more intraspecific competition.

Explanation

**Step-by-Step Solution:**

1. **Understanding Alien Species**: Alien species, also known as non-native or exotic species, are organisms that are introduced to a new environment where they do not naturally occur. This introduction can happen through various means such as human activity, accidental transport, or intentional release.

2. **Impact on Indigenous Species**: Indigenous species, or native species, are those that have evolved and adapted to a particular environment over a long period. The introduction of alien species can pose a significant threat to these indigenous species.

3. **Mechanism of Threat**: The primary reason alien species threaten indigenous species is due to the absence of natural predators. When an alien species is introduced into a new area, it often lacks the predators that would normally keep its population in check. This absence allows the alien species to proliferate rapidly.

4. **Competition for Resources**: Alien species may compete with indigenous species for resources such as food, space, and other ecological niches. However, the key factor that exacerbates this competition is the lack of natural predators for the alien species.

5. **Conclusion**: Therefore, the introduction of alien species poses a threat to the extinction of indigenous species primarily due to the absence of their natural predators, which allows the alien species to thrive and outcompete the native species.

6. **Correct Answer**: The correct answer to the question is option C: "Absence of their natural predators."

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