Which princely state was the only Muslim-majority state in the Punjab region?

The correct answer is: a) Malerkotla.

Malerkotla was a princely state in the Punjab region of British India. It was the only Muslim-majority state in the region. The state was founded in 1661 by Nawab Sher Mohammed Khan, a Mughal nobleman. The state was ruled by the Nawabs of Malerkotla until it was merged with the Indian Union

The other options are incorrect because they are not Muslim-majority states. Bahawalpur is a Muslim-majority state in Pakistan, but it is not located in the Punjab region. Loharu is a Hindu-majority state in Haryana, India. Khairpur is a Muslim-majority state in Sindh, Pakistan.