Explanation:

- Option 1: Prime Minister

- The Prime Minister does not have the constitutional power to specify or designate tribes as Scheduled Tribes. The role of the Prime Minister is primarily executive, overseeing the administration and implementation of policies.

- Option 2: President

- Correct Answer: The power to specify which tribes are to be treated as Scheduled Tribes in a particular state or Union Territory is constitutionally vested in the President of India, as per Article 342 of the Indian Constitution. The President issues notifications specifying these tribes, which can only be modified by an act of Parliament.

- Option 3: Governor

- Governors do not have the authority to designate Scheduled Tribes. Their role is more of a constitutional head at the state level, acting on the advice of the state’s council of ministers.

- Option 4: All of the above

- This option is incorrect as neither the Prime Minister nor the Governor has the power to designate Scheduled Tribes. Only the President holds this power, requiring legislative backing for changes.