Final answer:
The Earth Kingdom's cavalry predominantly uses war elephants, an ancient military option with distinctive strengths and weaknesses.
Step-by-step explanation:
The cavalry of the Earth Kingdom primarily uses the animal known as the war elephant. Although horses were often associated with cavalry in history, the Earth Kingdom, a fictional realm likely referenced in this context, seems to rely on a different type of cavalry. Elephantry, or units equipped with war elephants, have a storied history in military uses dating back to ancient times, such as in the Indian epic the Mahabharata or in the armies of the Persians against Alexander the Great. The use of elephants in the battlefield offered unique advantages, but they also had limitations, notably a propensity to panic under stress or when wounded.