The correct answer is option 'A' - Chinese travellers visited India primarily because they were interested in Buddhism. Let's explore this answer in detail.

Buddhism in China:
- Buddhism originated in India in the 6th century BCE and gradually spread to other parts of Asia, including China.
- In China, Buddhism started gaining popularity during the Han Dynasty (206 BCE - 220 CE) and continued to thrive during the subsequent dynasties.

Interest in Buddhism:
- Chinese intellectuals and scholars were fascinated by the teachings of Buddhism, which offered a different perspective on life, spirituality, and morality compared to traditional Chinese philosophies.
- The core teachings of Buddhism, such as the Four Noble Truths and the Eightfold Path, appealed to the Chinese intellectuals who sought answers to existential questions and a path to enlightenment.
- Buddhism was seen as a means to attain inner peace, spiritual liberation, and escape from the cycle of birth and death.

Pilgrimage to India:
- In order to deepen their understanding of Buddhism and learn from renowned Indian Buddhist monks and scholars, many Chinese travellers embarked on long journeys to India.
- These Chinese pilgrims undertook arduous and dangerous trips, often lasting several years, to reach the holy sites associated with the life of Buddha, such as Bodh Gaya (where Buddha attained enlightenment) and Sarnath (where Buddha delivered his first sermon).
- They were motivated by a strong desire to study Buddhist scriptures, engage in philosophical debates with Indian scholars, and bring back valuable Buddhist texts to China.

Notable Chinese travellers:
- One of the most famous Chinese travellers to India was Xuanzang (also known as Hiuen Tsang), who journeyed to India in the 7th century CE.
- Xuanzang spent around 17 years in India, visiting important Buddhist centers, studying under eminent Indian scholars, and collecting sacred Buddhist texts.
- He brought back hundreds of manuscripts to China, which greatly contributed to the spread and development of Buddhism in his homeland.

Conclusion:
Chinese travellers primarily visited India because they were deeply interested in Buddhism. They were driven by a desire to study Buddhist teachings, engage with Indian scholars, and bring back valuable texts to China. The exchange between ancient India and China played a significant role in the transmission and development of Buddhism in both countries.