Answer:
The correct answer is structural unemployment.
Explanation:
Structural unemployment refers to the phenomenon when a person or group of people with a similar skill set face unemployment or difficulty finding a job in their area of expertise because of changes/ advancements in technology or industrial reorganization, which in turn makes their job skills obsolete.
In this instance, Sally is experiencing structural unemployment because there is significantly reduced demand for underwater welders in the economy. In other words, her skills are now obsolete and no longer sought by employers. In this way, Sally is facing structural unemployment, and she instead decides to return to school to earn an economics degree, so that her skills matches her society's in demand skills, and she can find employment more easily.
