Sarah quits sandwich shop to seek engineering job; she is:

Structural unemployment arises when there is a mismatch between the skills of the workforce and the needs of the economy, often due to technological changes or shifts in market demand. Sarah's decision to leave her job for better opportunities in engineering does not reflect a mismatch in skills but rather a personal choice to pursue a different career path.

Seasonal unemployment is associated with jobs that only exist during certain times of the year. For instance, agricultural work may only be available during harvest months. Sarah's situation does not pertain to seasonal work, as her departure is motivated by a career change rather than the cyclical nature of employment.

Being "not in the labor force" refers to individuals who are neither employed nor actively seeking work, such as retirees or students. Since Sarah is actively seeking an engineering job, she is indeed part of the labor force, making this choice incorrect.