Topic: Fill in the Blank,

Best Answer Explained in Below-:

In the given sentence, the word that fills the blank should describe a scheme that is not only effective but also demonstrates creativity and cleverness in its design. The word "ingenious" (Option C) fits perfectly in this context, as it suggests that the scheme is highly innovative and resourceful, which is essential for addressing a complex issue like unemployment.

The other options do not convey an appropriate meaning for the context. "Irrelevant" (Option A) implies that the scheme has no significance or connection to the problem, which contradicts the desired outcome of reducing unemployment. "Unstable" (Option B) suggests that the scheme may not be reliable or sustainable, which would be counterproductive in effectively addressing unemployment rates. Lastly, "unfamed" (Option D) implies that the scheme lacks recognition or fame, which does not inherently speak to its effectiveness or cleverness.

Thus, "ingenious" stands out as the most suitable choice, indicating that the devised scheme is not only creative but also presents a smart approach to mitigating the serious issue of unemployment.