What does the expression "This year's rain is last year's snow" refer to?
A. Rain in the spring can sometimes freeze due to unseasonable temperatures.
B. Snow consists of water in the frozen state and this water becomes rain when subjected to higher temperatures.
C. The amount of water on Earth does not change and is cycled in an unending process despite its changing physical state.
D. The amount of rain and snow changes due to the changing amount of water that cycles through Earth's atmosphere.
