A stoppered bottle filled with water will break when it freezes because the volume of water increases when it freezes (C). When water freezes, it expands, forming ice crystals that occupy more space than liquid water. This expansion exerts tremendous pressure on the walls of the bottle, causing it to rupture. Option (A) is incorrect because the bottle doesn’t shrink when the water freezes. Option (B) is also incorrect because the volume of water actually increases upon freezing, contrary to decreasing. Option (D) is irrelevant as the ability of glass to conduct heat doesn’t directly relate to the bottle breaking when water freezes. The primary reason for the bottle breaking is the expansion of water upon freezing, which exerts pressure on the bottle’s walls, ultimately causing it to rupture. Therefore, the correct option is (C).