I am unable to solve this question in quantitative aptitude asked by a junior.
It's image ->
I thought that temperature will decrease as depth increase as there is no sunlight but that doesn't seems to help.
Answer is B.
Edit 1: Now posted on Puzzling Stackexchange.
Here are my two cents, not based on any specialized knowledge.
A. and D. show water at low density under a layer of higher density water. Surely that low density water is going to rise.
C. shows a sudden shift of temperature at 10 meters. Surely that is unstable.
B. shows a gradual change of temperature with depth. And the surface is near zero degrees Celsius, so there may be a layer of ice at the top. I suppose this could be a stable situation.