In which of the following examples has a chemical reaction occurred?
A .After putting liquid batter into a hot pan, the batter solidifies and begins to turn brown.
B .After turning on a blender filled with fruits, the fruit is chopped up and mixed together.
C. After taking a tray filled with ice cubes out of the freezer, the cubes begin to melt.
D. After adding a spoonful of sugar to a mug of hot coffee, the sugar dissolves completely.