Scientists on the east coast conducted an experiment to chart the effects of acid rain on contained bodies of water, such as lakes and ponds. They added bromcresol green, an indicator that is blue in neutral solutions and yellow in acid solutions to water samples from both limestone bottom lakes and granite bottom lakes. They placed the water/indicator samples in separate beakers, one lined with limestone rocks, the other with granite. The scientists added equal amounts “acid rain” to the lake samples and the indicator, in both cases, turned yellow. Gradually, the limestone sample returned turned blue again, indicating that it had returned to neutral. The granite lake sample remained acidic.

Why did the limestone-based "lake" return to neutral?
A) The calcium carbonate ions combine with water to lower the pH.
B) The calcium carbonate in the limestone helped to neutralize the acid rain.
C) The calcium carbonate in the limestone lowered the pH of the water sample.
D) The acid rain reacted with the granite and caused it to become even more acidic.