The correct answer is b) Patiala.
The Sikh Confederacy was a political and military alliance of Sikh states in the Punjab region of India. It was formed in 1765 by Maharaja Ranjit Singh, the founder of the Sikh Empire. The Confederacy was a loose alliance of independent states, each with its own ruler. However, they all agreed to cooperate with each other in matters of defense and foreign policy.
The state of Patiala was one of the most important members of the Sikh Confederacy. It was ruled by the Bhasin family, who were descendants of Guru Gobind Singh, the tenth Sikh Guru. The Bhasins were powerful and influential rulers, and they played a key role in the Confederacy.
The other three options are also princely states that were part of the Sikh Confederacy. However, they were not as important as Patiala. Faridkot was ruled by the Faridkot family, who were descendants of Guru Nanak Dev, the first Sikh Guru. Kapurthala was ruled by the Kapurthala family, who were descendants of Guru Amar Das, the third Sikh Guru. Nabha was ruled by the Nabha family, who were descendants of Guru Ram Das, the fourth Sikh Guru.
All four of these princely states were eventually annexed by the British Indian Empire in the 19th century. However, they played an important role in the history of the Sikh Confederacy.