Bahadur Shah's Alliance with Chatarsal:
Bahadur Shah, also known as Muhammad Mu'azzam, was the Mughal emperor who ruled from 1707 to 1712. During his reign, he faced various challenges from different regional powers. One of his strategies to maintain control and stability was to form alliances with local chiefs and rulers.

One such alliance was formed with Chatarsal, the Bundela chief. The Bundelas were a Rajput clan that held significant power in the region of Bundelkhand, which is present-day Madhya Pradesh and Uttar Pradesh in India. Chatarsal had established himself as a prominent ruler in Bundelkhand and had a considerable army at his disposal.

The Role of Chatarsal:
Chatarsal played a crucial role in supporting Bahadur Shah against his rivals. He provided Bahadur Shah with military assistance and resources. This alliance was beneficial for both parties. Bahadur Shah gained a powerful ally who could help him counter his enemies, and Chatarsal received protection and support from the Mughal Empire.

The Jat Chief's Involvement:
In addition to Chatarsal, a Jat chief also joined Bahadur Shah in his campaign against Banda Bahadur. Banda Bahadur was a Sikh military commander who had established a short-lived Sikh state in Punjab. He posed a significant threat to the Mughal Empire, and Bahadur Shah sought to defeat him and regain control over Punjab.

The Jats were an agricultural community that inhabited the regions of present-day Haryana, Uttar Pradesh, and Rajasthan. They had a long history of resistance against Mughal rule and had formed their own independent kingdoms at times. The Jat chief who joined Bahadur Shah in the fight against Banda Bahadur was Suraj Mal.

The Significance of Suraj Mal's Support:
Suraj Mal was the ruler of Bharatpur, a Jat state in present-day Rajasthan. He was known for his military prowess and strategic abilities. Suraj Mal's decision to support Bahadur Shah was crucial in the efforts to suppress Banda Bahadur's rebellion.

Suraj Mal's forces played a significant role in the battles against Banda Bahadur's Sikh forces. His army's involvement and coordination with the Mughal forces contributed to the ultimate defeat of Banda Bahadur and the restoration of Mughal authority in Punjab.

Therefore, the correct answer is option 'B' - Suraj Mal. He was the Jat chief who joined Bahadur Shah in fighting against Banda Bahadur, alongside the alliance with Chatarsal.