The correct answer is option 'D' - Rhesus macaque.

The Wildlife Protection Act, 1972 is an important legislation in India that aims to protect and conserve wildlife and their habitats. It categorizes different species of animals into various schedules based on their level of protection needed. Schedule 2 of the Wildlife Protection Act includes species that are not necessarily endangered but still need to be protected and conserved.

Here is a detailed explanation of the correct answer:

1. Schedule 2 of the Wildlife Protection Act, 1972:
- Schedule 2 of the Wildlife Protection Act, 1972 includes animals that are not necessarily endangered but still require protection and conservation measures.
- The animals listed under this schedule are considered to be of ecological, scientific, or economic importance, and their conservation is necessary to maintain a balanced ecosystem.

2. Rhesus macaque:
- Rhesus macaque, also known as the Indian rhesus monkey, is a species of Old World monkey native to South Asia.
- It is listed under Schedule 2 of the Wildlife Protection Act, 1972, indicating the need for its protection and conservation.
- Rhesus macaques play a significant role in the ecosystem as they are important seed dispersers and contribute to forest regeneration.
- They are also used in scientific research and have contributed to advancements in medical science, particularly in the field of immunology.

3. Importance of conservation:
- The inclusion of Rhesus macaque in Schedule 2 highlights the importance of conserving this species to maintain a balanced ecosystem.
- Conservation measures help in safeguarding the population of Rhesus macaques and ensuring their survival in their natural habitats.
- This species is also protected to prevent any illegal trade or exploitation, which could lead to a decline in their population.

In conclusion, the correct animal listed under Schedule 2 of the Wildlife Protection Act, 1972 is the Rhesus macaque. Its inclusion in this schedule emphasizes the need for its protection and conservation to maintain a balanced ecosystem and prevent any illegal trade or exploitation.