Alternate approach - combine the sex-wise range instead of recalling a single figure:
Laccifer lacca shows sexual size dimorphism: males are smaller, roughly 0.6 to 1.0 mm, while females are larger, roughly 1.0 to 1.5 mm.
A question asking for the size range of a "healthy adult" without specifying sex must be read as covering the full population, i.e. the lower bound of the male range through the upper bound of the female range.
Combining 0.6 mm (male minimum) with 1.5 mm (female maximum) gives an overall span of 0.6-1.5 mm, which matches only one listed option and rules out the narrower or larger ranges given.