The amount of matter will be the same - matter cannot be destroyed or created.
The state of matter could change, however, e.g. solid to liquid.
The amount of matter stays same as water changes state.
When water changes its state, inner composition and arrangements of molecule will change but amount of matter stays same. when water from its liquid state changes to solid movement of molecule is almost zero. and arrangement of molecules is stable( in case of water, density of its liquid state is more than its solid state). When water convert in gaseous state randomness of molecules increase but amount of matter remains same.
According to law of conservation of matter, mass or matter can never be created nor it can be destroyed as it can only be transformed from one form to another.
For example, freezing of water changes liquid form of water into solid form.
Therefore, state of matter can be changed but amount of matter will remain the same.
Thus, we can conclude that the amount of matter stays the same as water changes state.
C, because matter can not be created or destroyed.