Johnnie's father worked his entire career in the automotive manufacturing industry in Michigan. When Johnnie entered the workforce, the auto industry was in decline, so he instead found a professional career in the booming information technology sector, an industry that did not exist when his father began his career. This is an example of

a. structural mobility.
b. horizontal mobility.
c. exchange mobility.
d. social reproduction.

"Structural mobility" refers to a kind of Social Mobility that happens when the hierarchy experiences some changes in its stratification. This causes some occupations to rise or decline in the social hierarchy.

In the situation above, the automotive manufacturing industry that Johnnie's father worked for in the past declined while the information sector rose. This causes structural changes, thereby allowing Johnnie to get hired immediately in the information technology sector than in the automotive manufacturing industry.

This also means that the change which occurred doesn't come from the individual but from the society.

So, this explains the answer.