Explain how water erosion by groundwater can form a cave

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Working slowly over many years, ground water travels along small cracks. The water dissolves and carries away the solid rock gradually enlarging the cracks, eventually forming a cave. Ground water carries the dissolved minerals in solution. The minerals may then be deposited, for example, as stalagmites or stalactites.

so whats the answer? ?

b.

developed countries have tended to improve the environment, while developing countries have tended to damage it.