Figure A shows the column is cold to start but warm in the mid levels to the surface, Precipitation starts as snow and melts as it falls through the warm layer, surface is all Rain.

Figure B shows the column is cold to start, a warm layer in the middle melting the snow flakes..The surface layer is cold so as the rain reaches the ground it than refreezes. FREEZING RAIN

Figure C shows a cold column to start,,than a warm mid level and than a deeper shallow level..Snow starts than melts, as the rain drop falls through a deeper layer of cold it freezes into an ice pellet reaching the ground. SLEET

Figure D shows the column cold from top to bottom..Snow starts and can fall right through the cold column to the surface. ALL SNOW