Final answer:
Social mobility is highly unlikely in closed systems of stratification such as slavery, estate, and caste systems because these systems do not allow for movement between different social levels or relations.
Step-by-step explanation:
Social mobility is not probable in a closed system of stratification. In closed systems, such as slavery, estate, and caste systems, changes in social position are typically not possible, as these systems are based on ascribed status or birth. Stratification systems that are closed do not permit movement between different social levels or social relationships between these levels, making social mobility highly unlikely.
On the other hand, open systems, like class systems and meritocracies, allow for some degree of social mobility. Class systems are open to movement based on factors such as wealth, income, education, and occupation, whereas meritocracies confer standing based on personal effort and merit, rewarding hard work and achievement.