Final answer:
The water level in the tube changed due to the expansion of air in the bottle when a hot wrap was applied, which is an effect of thermal expansion.
Step-by-step explanation:
When the student put the hot wrap on the bottle causing the water level in the tube to change, the correct explanation for this phenomenon is A) Expansion of air in the bottle. Thermal expansion is the change in volume or size of a system due to temperature changes. This principle applies to gases as in this case with the air in the bottle. When exposed to heat from the hot wrap, the air inside the bottle expands due to an increase in kinetic energy, which in turn decreases the air's density compared to the surrounding air. This leads to an increase in volume and can push water out of the bottle if the bottle is connected to a tube, thereby changing the water level within the tube.