Step 1: Understanding the taxonomic hierarchy.
The highest taxonomic category in biological classification is the kingdom. It is the broadest classification, and organisms are grouped into one of the five kingdoms.
Step 2: Analyzing the options.
(A) species: Incorrect. Species is the lowest and most specific level of classification.
(B) division: Incorrect. Division is a taxonomic rank used in plant classification, but it is not the highest category.
(C) genus: Incorrect. Genus is a category above species, but it is not the highest.
(D) kingdom: Correct. Kingdom is the highest taxonomic category in the biological classification system.
Step 3: Conclusion.
The correct answer is (D) kingdom, as it is the highest taxonomic category.