The correct answer is: d) All of the above.
Dispossessed zamindars were Indian landowners who had been stripped of their land and power by the British East India Company. They were a potential source of unrest, as they had a vested interest in overthrowing British rule.
Disgruntled sepoys in native regiments were Indian soldiers who were unhappy with their pay and conditions. They were also a potential source of unrest, as they had the means and opportunity to carry out an uprising.
Muslim preachers were a powerful force in Indian society. They could incite their followers to violence, and they were often critical of British rule. They were therefore a potential source of unrest.
In conclusion, all of the above groups were potential sources of unrest for the British in India.