**The Ruling Period of Prithviraj III**

Prithviraj III, also known as Prithviraj Chauhan, was a ruler of the Chauhan dynasty in medieval India. He is often considered one of the greatest warriors in Indian history. The correct answer to the question is option 'A', which states that his ruling period was from 1178 to 1192. Let's delve into the details to understand why this is the correct answer.

**1. Background Information:**
- Prithviraj III was born in 1166 CE in Ajmer, Rajasthan, to King Someshvara and Queen Karpuradevi.
- He ascended the throne at a young age, following the death of his father.
- Prithviraj III is renowned for his valor and military prowess, particularly in his battles against the Muslim invader Muhammad Ghori.

**2. Rise to Power:**
- Prithviraj III became the ruler of the Chauhan dynasty in 1178 CE.
- He inherited a kingdom that was already well-established and prosperous. Under his rule, he aimed to expand its territories and consolidate his power.

**3. Battles with Muhammad Ghori:**
- Prithviraj III's most famous battles were against Muhammad Ghori, the Sultan of the Ghurid Empire.
- The first battle between the two took place in 1191 CE at the Tarain region of present-day Haryana.
- Prithviraj III emerged victorious in this battle, capturing Ghori but eventually releasing him out of generosity.
- However, Ghori returned the following year with a larger army, leading to the Second Battle of Tarain in 1192 CE.

**4. Defeat and End of Rule:**
- The Second Battle of Tarain proved to be a turning point in Prithviraj III's reign.
- Despite initially having the upper hand, he was ultimately defeated by Ghori's forces, leading to his capture and imprisonment.
- Prithviraj III's rule effectively ended with his defeat in 1192 CE, and he remained a captive of Ghori until his death.

**Conclusion:**
Prithviraj III, also known as Prithviraj Chauhan, ruled from 1178 to 1192 CE. His reign was marked by his military prowess and his battles against the invading forces of Muhammad Ghori. Despite his initial victory, he was ultimately defeated and captured in the Second Battle of Tarain, leading to the end of his rule.