An iron bar at 325 k is placed in a sample of water. the iron bar gains energy from the water if the temperature of the water is
(1) 65 k (3) 65°c
(2) 45 k (4) 45°c

So what you need to do is to have all your answers in the same unit as the one in the question which is K then look for the one that is greater than that in the question because only then will it absorb heat from the water.

temp. of rod:  325K
(1)  65 K
(2) 45 K
(3) 65° C  =  (65 + 273) K = 338 K
(4) 45° C  =  (45 + 273) K = 318 K

⇒ option 3 is the answer

Most smaller stars don't have a radiative zone.