Kosal, Anga, Kashi and Vajji were all:

Correct option is B

The correct answer is: (b) part of 16 Mahajanapadas

Explanation:
Kosal, Anga, Kashi, and Vajji were among the famous 16 Mahajanapadas that flourished in India during the 6th century BCE. These Mahajanapadas were powerful territorial states that emerged in northern India as a result of socio-political and economic changes, particularly urbanization and the growth of trade and agriculture. The Buddhist text Anguttara Nikaya provides a detailed list of these Mahajanapadas.

• Kosal: Region corresponding to present-day eastern Uttar Pradesh.

• Anga: Corresponded to parts of present-day Bihar.

• Kashi: Region around present-day Varanasi.

• Vajji: A confederacy led by the Licchavis, located in north Bihar.

Thus, they were not individually conquered by the rulers mentioned in other options but collectively formed a crucial part of the political landscape of ancient India.

Information Booster:

• The 16 Mahajanapadas are mentioned in Buddhist and Jain texts.

• Magadha, Kosal, Vatsa, and Avanti were the most powerful Mahajanapadas.

• Vajji was known for its early form of republican governance.

• King Ajatshatru of Magadha waged war against the Vajji confederacy.

• The concept of Mahajanapadas marked the second urbanization in India.

• The rise of the Mahajanapadas set the foundation for larger empires like Magadha.

Additional Information:

• conquered by King Ajatshatru: King Ajatshatru (reigned c. 492–460 BCE) expanded Magadha by waging wars against neighboring states like Vajji, but he did not conquer all Kosal, Anga, Kashi together.

•  ruled by King Harshvardhan in 6th century AD: Harshavardhana ruled in the 7th century AD, not the 6th century BCE, and mainly controlled north India after the decline of the Gupta Empire.

• conquered by King Jaichand: King Jaichand was a ruler of Kannauj in the 12th century AD, much later than the Mahajanapada period.