Answer:
The correct option is C.
Step-by-step explanation:
If the system is present in the dynamic equilibrium, then the rate of sublimation of the NH4CI crystals is equal to the rate of production if the NH4CI vapors.
A dynamic equilibrium is defined as the reversible reaction repel to change its ratio of products, and reactants, but at equal rate substances keep moving between the chemicals, and there is no net change occurs.
So, the correct answer is option C. (The rate of sublimation of the NH4CI crystals is equal to the rate of solidification of the NH4CI vapors).