Which of the following statements best defines the law of conservation of mass?

Question

$\begin{array}{1 1} \text{(a)Mass cannot be created but it can be destroyed under extreme pressures.} \\ \text{(b) Mass cannot be conserved during a chemical reaction; a little bit of mass is always lost.} \\ \text{(c) The mass of a closed system cannot change over time; mass cannot be created nor destroyed.} \\ \text{(d) When added to a system, energy can destroy mass.} \end{array}$