Final answer:
The staunch followers of Guru Gobind Singh Ji are called the Tat Khalsa, marking option 'a' as the correct answer. Sikhism rejects the caste system and is deeply rooted in the belief of universal equality, which opposes the Indian caste hierarchy where the Brahmans are at the top.
Step-by-step explanation:
The group of staunch followers of Guru Gobind Singh Ji, the tenth Sikh Guru, was called the Khalsa. This community was founded on Baisakhi Day, March 30, 1699, and the Khalsa are characterized by their distinct features and dedication to the Sikh faith. Specifically, the followers are known as the Tat Khalsa, representing option 'a' from the provided choices. The Khalsa is a group of Sikh warriors known for their bravery and their role in resisting Mughal authority, particularly during the time of Aurangzeb who executed the ninth Guru, Guru Tegh Bahadur, and sought to undermine Sikh autonomy.
Guru Tegh Bahadur, mentioned in the context, was the ninth Guru of the Sikhs, adhering to the Sikh faith, which would answer question 4 as 'a. Sikh'. The highest tier in the traditional Indian caste system is occupied by the Brahmans, making 'd. Brahman' the correct answer to question 18. Sikhism itself was founded by Guru Nanak Dev Ji and stands apart from the caste system, promoting equality among all people.