Introduction:
Maintaining ecological balance is crucial for the sustainability of ecosystems. Animals play an important role in maintaining this balance through various ecological processes.

Explanation:
1. Wild Animals:
Wild animals are those that live in their natural habitat without any human interference. They play a significant role in maintaining ecological balance in the following ways:

- Prey-predator relationship: Wild animals maintain ecological balance by regulating the population of their prey species. For example, predators like lions, tigers, and wolves control the population of herbivores like deer, ensuring that they do not overgraze the vegetation.

- Seed dispersal: Many wild animals such as birds, bats, and rodents help in seed dispersal. They consume fruits and disperse the seeds through their droppings, promoting plant diversity in different areas.

- Pollination: Insects, birds, and bats play a crucial role in pollination. They transfer pollen from one flower to another, aiding in the reproduction of plants and ensuring the production of fruits and seeds.

- Decomposition: Scavengers and decomposers like vultures, worms, and fungi contribute to the decomposition of dead organisms. They break down organic matter, releasing nutrients back into the ecosystem and maintaining nutrient cycling.

2. Domestic Animals:
Domestic animals are those that are kept by humans for various purposes such as agriculture, transportation, and companionship. While domestic animals primarily serve human needs, they indirectly contribute to ecological balance in the following ways:

- Agricultural activities: Domestic animals like cows, goats, and sheep are used for agriculture. They help in plowing fields, fertilizing the soil through manure, and controlling weed growth. These activities support sustainable farming practices.

- Pollination: Some domestic animals like honeybees are kept for honey production. These bees help in pollinating plants, thereby supporting plant reproduction and maintaining biodiversity.

- Food chain support: Domestic animals are a part of the food chain, providing a source of food for predators in the wild. For example, farm animals like chickens and cows serve as prey for wild carnivores, maintaining the natural balance in the ecosystem.

Conclusion:
Both wild and domestic animals play essential roles in maintaining ecological balance. While wild animals contribute directly through their natural behaviors and interactions, domestic animals indirectly support ecological balance through their involvement in agricultural practices and food chains. Therefore, option 'A' - Wild animals, is the correct answer.