In India, why are some nuclear reactors kept under "IAEA Safeguards" while others are not?

In India, why are some nuclear reactors kept under "IAEA Safeguards"…

Some use uranium and others use thorium
Some use imported uranium and others use domestic supplies
Some are operated by foreign enterprises and others are operated by domestic enterprises
Some are State-owned and others are privately-owned

Answer

(a) Some use uranium and others use thorium — Incorrect. IAEA safeguards in India are not based on uranium vs thorium fuel; they are based on whether a facility is placed in the civilian safeguarded list.
(b) Some use imported uranium and others use domestic supplies — Correct. After the India-specific safeguards arrangement, reactors using imported fuel/under civilian cooperation are kept under IAEA safeguards to ensure civilian use; strategic reactors using domestic resources may remain outside safeguards.
(c) Some are operated by foreign enterprises and others are operated by domestic enterprises — Incorrect. Indian nuclear power reactors are operated by Indian entities; foreign operation is not the basis for safeguards.
(d) Some are State-owned and others are privately-owned — Incorrect. Nuclear power generation in India is essentially under state control/public sector, not divided into private vs state ownership for this purpose.

Answer: (b)