Assume that water filling a crack in a rock undergoes cycles of freezing and melting. which of the following statement is true? a. water expands as it melts, causing the crack walls to be pushed apart. b. water expands as it freezes, causing the crack walls to be pushed apart. c. water shrinks as it freezes, causing the crack walls to be drawn closer together. d. water shrinks as it melts, causing the crack walls to be pulled closer together.