The correct answer is option 'B' - Compositions.

The Nayanars were a group of poet-saints from South India who lived between the 5th and 10th centuries CE. They were devotees of Lord Shiva and composed devotional hymns known as Tevaram in Tamil. These hymns express their deep love and devotion for Lord Shiva and also reflect their strong opposition to Buddhism and Jainism.

The Nayanars' opposition to Buddhism and Jainism is particularly evident in their compositions, which serve as a means of expressing their thoughts and beliefs. Here's an explanation of why the correct answer is 'B' - Compositions:

1. Context of the Nayanars:
The Nayanars lived during a time when Buddhism and Jainism were prominent religions in South India. These religions had gained significant influence and were seen as a challenge to the existing Vedic and Brahmanical traditions.

2. Poetic Expression:
The Nayanars used their compositions as a medium to express their thoughts, emotions, and beliefs. Their hymns were not only a form of artistic expression but also a way to propagate their religious ideology.

3. Opposition to Buddhism and Jainism:
In their compositions, the Nayanars expressed their strong opposition to Buddhism and Jainism. They criticized the beliefs and practices of these religions, often contrasting them with the glory and supremacy of Lord Shiva.

4. Exposing the "False Paths":
The Nayanars saw Buddhism and Jainism as "false paths" that deviated from the true path of devotion to Lord Shiva. Through their compositions, they aimed to expose what they perceived as the shortcomings and limitations of these religions.

5. Promoting Shaivism:
The Nayanars used their compositions to promote Shaivism, a sect of Hinduism that worships Lord Shiva as the supreme deity. They praised the greatness and power of Lord Shiva, emphasizing his role as the ultimate source of salvation and liberation.

In conclusion, the Nayanars' opposition to Buddhism and Jainism is particularly evident in their compositions. Through their hymns, they expressed their strong criticism of these religions and promoted the worship of Lord Shiva.