The best choice to add context to the introduction while smoothly transitioning into the paper's subtopics about trade schools and the worker shortage is:
B. Skilled trade positions are plentiful. Less plentiful are the men and women with the qualifications to fill them.
This sentence directly addresses the core issue the paper is discussing— the disconnect between the demand for skilled labor and the supply of qualified workers— which aligns well with the introduction's focus on the need for trade schools.