Which of the statements below is/are not true? a a chemical equation describes quantities of substances consumed and produced by a chemical reaction. b. to balance a chemical equation means to determine the smallest positive integer numbers of molecules of each substance involved into the reaction c. to set up a linear system, we use the fact that the atoms are neither destroyed nor created in a chemical reaction. d a homogeneous linear system for balancing a chemical equation may have only the trivial solution. e. network flow assumption: the total flow in a network (or junction) is equal to the total flow out of the network (or junction)