Final answer:
The largest group in Linnaeus's seven-level classification system is the kingdom, which is the most inclusive taxonomic category.
Step-by-step explanation:
The largest group in Linnaeus's seven-level classification system is the kingdom. The hierarchy of taxonomic classification within the Linnaean system begins with the broad and inclusive category of kingdom, followed by more specific categories such as phylum, class, order, family, genus, and species, with species being the most specific and exclusive grouping. As such, the answer to the student's question is (a) Kingdom.