Final answer:
The only son of Guru Arjan Dev Ji was Guru Hargobind Ji, who was the sixth Sikh Guru after his father, making A) Guru Hargobind Ji the correct answer. Sikhism, the religion of Guru Tegh Bahadur, is a monotheistic faith founded by Guru Nanak Dev Ji.
Step-by-step explanation:
The only son of Guru Arjan Dev Ji was Guru Hargobind Ji. Guru Arjan Dev Ji was the fifth of the eleven Sikh Gurus, the leaders and founders of Sikhism. He was succeeded by his son, Guru Hargobind Ji, making the correct answer to the question A) Guru Hargobind Ji.
Guru Tegh Bahadur, mentioned in the context, was a leader of the Sikh faith, and he became the ninth Sikh Guru. He was executed by the Mughal emperor Aurangzeb, who clashed with the Sikhs because of their resistance to his authority. The Sikh religion was founded by Guru Nanak Dev Ji, and it is a monotheistic faith that emerged in the fifteenth century in the Punjab region of northwestern India. Guru Tegh Bahadur's execution inspired greater resistance against the Mughal rule and further solidified the identity of the Sikh community.