To effectively explain the context for the paper's subtopics, the most suitable sentences to add to the introduction are:
B. Skilled trade positions are plentiful. Less plentiful are the men and women with the qualifications to fill them.
This option clearly sets up the issue that the paper will address regarding the shortage of qualified workers in skilled trades, which aligns with the primary argument for the need for more trade schools. By stating the availability of skilled positions and the lack of qualified individuals, it provides a direct segue into the discussion about trade schools and their role in filling that gap.