a) there is no longer any net change in the concentration of products and reactants
Explanation:
There is dynamic equilibrium when in a reversivble reaction stop changing your reagents / product ratio; but the substances move at an equal rate; System properties do not change over time.
The system is in dynamic equlibrium if it has all three types of equilibrium:
mechanic equilibrium: if there is no net force applied to the system
thermal equilibrium: constant temperature.
material equilibrium: the composition on the system does not change.
