**Explanation:**

**Livestock Population Distribution**

The livestock population refers to the total number of domesticated animals raised for various purposes such as meat, milk, eggs, and other agricultural products. The distribution of livestock population varies across different countries based on factors such as climate, agriculture practices, economic conditions, and cultural preferences.

**Livestock Population in India**

India has a significant livestock population and is one of the largest producers of livestock products in the world. The country has a diverse agricultural system, with a significant number of farmers engaged in livestock farming. Livestock in India include cattle, buffalo, sheep, goats, pigs, and poultry. These animals are reared for milk, meat, eggs, wool, and other products. The livestock sector plays a crucial role in India's rural economy, providing livelihoods to millions of people.

**Livestock Population in China**

China is another country with a substantial livestock population. The Chinese livestock sector is diverse and includes various species such as pigs, poultry, cattle, sheep, and goats. China is the largest producer and consumer of pork in the world, and pork is a staple meat in the Chinese diet. The country also has a significant poultry industry, with high consumption of chicken and eggs. Livestock farming is an essential component of China's agricultural sector, contributing to food security and rural development.

**Combined Livestock Population in India and China**

Considering the large population size of both India and China, it is not surprising that the combined livestock population in these two countries exceeds 70% of the global total. With India and China being the two most populous countries in the world, their livestock sectors are substantial and contribute significantly to global livestock production.

India and China have a long-standing tradition of livestock rearing, and the demand for livestock products in these countries is high due to their large populations. The agricultural practices, climate, and cultural preferences in both countries are conducive to livestock farming, resulting in a substantial livestock population.

Therefore, the correct answer to the given question is option 'D' - India and China, as these two countries together account for more than 70% of the global livestock population.