The outbreak of COVID-19 resulted in a health crisis and a drop in economic activity that were without ______________ in history. While containing and ______________ the spread of the virus was the first priority of public authorities, reducing the ______________ of the disease and limiting the pressure on healthcare systems were also considered equally important.

The passage describes the unprecedented nature of the COVID-19 pandemic and outlines the dual priorities of managing both the spread and impact of the virus.  It is evident from the context that the first blank requires a noun that means "prior example," the second blank requires a verb that means "reducing severity," and the third blank requires a noun that means "frequency of occurrence."

The only word among the available choices that exactly fills in the first blank is "precedent" (Option B), which means "a prior instance that establishes a pattern" and thus captures the historical singularity of COVID-19's impact. "Similarity"(Option A) deviates from the intended meaning, "Equivalent"(Option C) suggests comparable magnitude but not temporal precedence, and  "Parallel"(Option D) suggests simultaneity rather than historical precedence.

Since "making less severe" is the precise strategy required for viral containment, "mitigating" (Option B) is the best option for the second blank. "Eradicating" (Option C) implies total elimination, which is unrealistic for an initial response; "controlling" (Option D) lacks the subtlety of severity reduction; and "combating" (Option A) is overly general.

"Incidence" (Option B), which particularly refers to the "frequency of occurrence" of disease cases, is the best fit for the third blank. In this context, "outbreak" (Option D) is superfluous, "prevalence" (Option A) refers to the overall disease burden rather than the occurrence rate, and "toll" (Option C) refers to the cumulative impact rather than frequency.

Therefore, Option B is the uniquely correct choice.