The first option because in the water cycle, water does not change chemically but, it changes its physical form throughout the cycle. In other chemical cycles ,the element (such as carbon) changes chemically throughout its cycle making it the main difference between the water cycle and other chemical cycles.
Other cycles change their structural form often, but water does not change it's structural form in the water cycle, which is H2O so that is one main difference between the water cycle and oither checmical cycles. So, your answer is A.
