Why Does Ice Form at the Surface of a Body

Why does ice form at the surface of a body of fresh water instead of at the bottom?

A) Initial freezing requires the presence of air in order to form the ice lattice, thus the surface water will become solid first.
B) Intermolecular forces are greater at the surface allowing the surface molecules to form the solid phase more quickly.
C) Water "near" the freezing point of 0°C is less dense than warmer water, and the colder water will "float" on the warmer water. This allows ice to form at the surface.
D) All of the above are true.