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^(0)C` to `4^(0)C` is negative and above `4^(0)C` it is positive. This behaviour of water shapes the freezing of lakes as the atmospheric temperature goes down and it has an extremely important effect on plant and animal life in lakes.
As the atmospheric temperature goes down. but it is still above `4^(0)C` :

Options

A. cooled water at the surface flows downward because of its greater density.
B. cooled water at the sruface does not flow downward and remains at the surface because of its smaller density
C. cooled water at the surface, thought 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