Structural mobility occurs when:

an individual moves up the class ladder

an individual moves down the class ladder

a large group moves up or down the class ladder due to societal changes

a member of a family belongs to a different class than his or her siblings

The correct answer is C. A large group moves up or down the class ladder due to societal changes

Explanation:

In sociology, the word "mobility" or "social mobility" describes a change in the social structure or stratification system usually as people move to a higher social class or level or to a lower one. Additionally, this mobility is usually caused due to changes in society and can be of different types as if mobility involves a change in the class through generations it is called intergenerational mobility but when it involves a large group that moves up or down the structure of society or the class ladder this is called structural mobility, which is caused by major societal changes that affect not only an individual but a large group. Therefore, structural mobility occurs when a large group moves up or down the class ladder due to societal changes.