Most substances contract on freezing . However, water does not belong to this category. We know that water expands on freezing. Further , coefficient of volume expansion of water in the temperature range from `0^(@)C` to `4^(@)C` is negative and above `4^(@)C` it is positive . This behaviour of water shapes the freezing of lakes as the atmospheric temperature goes down and it is still above `4^(@)C`.
As the atmospheric temperature goes below `4^(@)C`

Options

A. Cooled water at the surface flows downward because of its greater density
B. Cooled water at the surface does not flow downward and remains at the surface because its smaller density
C. Cooled water at the surface , through it remains on the surface because of its smaller density, will conduct heat from the interior to the atmosphere
D. Cooled water at the surface flows to the bottom because of its smaller density

Answer

A

Explanation

At temperature above `4^(@)C`, temperature of water above is less as compared to below as water is heated by radiation of longer wavelength.