To effectively enhance the context for the paper's subtopics, the best sentences to add to the underlined introduction would be:
B. Skilled trade positions are plentiful. Less plentiful are the men and women with the qualifications to fill them.
This sentence directly addresses the shortage of qualified workers in skilled trades, setting the stage for discussing the need for more trade schools and emphasizing the gap that the paper aims to explore.
Additionally, while option A also provides useful information about trade schools, option B succinctly encapsulates the issue that the paper will delve into regarding employment and the demand for skilled workers.