The correct answer is (a). Water expands on freezing.
When water freezes, it expands because the molecules arrange themselves into a crystal structure that takes up more space than the liquid water. This expansion can cause the bottle to break if it is not strong enough to withstand the pressure.
Option (b) is incorrect because the bottle does not contract at freezing point. In fact, the bottle may expand slightly due to the pressure of the expanding water.
Option (c) is incorrect because the temperature outside the bottle is not necessarily more than inside. In fact, the temperature inside the bottle may be much lower than the temperature outside, which is why the water freezes.
Option (d) is incorrect because water expands on heating, not on freezing.