Adivasis, or indigenous people of India, have a rich cultural and religious heritage. Throughout history, they have been influenced by various surrounding religions. The correct answer is option 'C', which states that Adivasis have been influenced by Shakta, Buddhist, Vaishnav, Bhakti, and Christianity religions. Let's explore each of these influences in detail.

1. Shakta:
- Shakta refers to the worship of the divine feminine energy, primarily represented by various forms of the goddess Devi.
- Adivasis have been influenced by Shakta practices, which involve rituals, festivals, and prayers dedicated to goddesses like Durga, Kali, and Lakshmi.
- These practices reflect the reverence for nature and the belief in the power of the divine feminine.

2. Buddhist:
- Buddhism, founded by Gautama Buddha, has also influenced Adivasis.
- Buddhism emphasizes the principles of non-violence, compassion, and mindfulness.
- Adivasis have adopted Buddhist practices such as meditation, chanting, and following the teachings of Buddha.
- These practices promote inner peace, self-reflection, and harmony with others.

3. Vaishnav:
- Vaishnavism is a major branch of Hinduism that worships Lord Vishnu and his avatars like Rama and Krishna.
- Adivasis have embraced Vaishnav practices, including the chanting of Vishnu's names, singing devotional songs, and observing festivals like Diwali and Janmashtami.
- These practices reflect their devotion to Lord Vishnu and their belief in his divine presence.

4. Bhakti:
- Bhakti refers to the devotional aspect of Hinduism that emphasizes a personal and emotional connection with the divine.
- Adivasis have been influenced by Bhakti practices, which involve singing bhajans (devotional songs), participating in kirtans (devotional gatherings), and expressing their love and devotion to their chosen deities.
- These practices allow Adivasis to experience a deep spiritual connection and express their faith through devotional acts.

5. Christianity:
- Christianity, introduced to India by European missionaries, has also influenced Adivasis.
- Many Adivasis have embraced Christianity and its teachings, attending church services, participating in Christian festivals, and following the Bible.
- Christianity provides a different religious perspective to Adivasis, emphasizing the teachings of Jesus Christ, love, and forgiveness.

In conclusion, Adivasis have been influenced by various surrounding religions, including Shakta, Buddhist, Vaishnav, Bhakti, and Christianity. These influences have shaped their religious practices, rituals, festivals, and beliefs, reflecting the diversity and richness of their cultural heritage.