"Clouds and gases travel westward, so suddenly, in winter and summer; Water springs flow eastward, day and night, inexhaustible ... "This paper mainly involves the water cycle.

"Clouds and gases travel westward, so suddenly, in winter and summer; Water springs flow eastward, day and night, water is inexhaustible, and water is dissatisfied ... "Clouds and gas travel westward, so suddenly, endless winter and summer refer to water vapor transportation in the water cycle; Water springs flow eastward day and night, which is inexhaustible and not satisfied with the surface runoff and underground runoff in the water cycle.

Therefore, choose: B.