What was the importance of 'mode of nutrition' in Whittaker's five-kingdom classification?

Correct answer: It was a major scientific basis for defining different kingdoms

Direct answer: B. Whittaker used mode of nutrition as a major criterion because organisms obtain food in fundamentally different ways. Plants are generally autotrophic and manufacture food, fungi are heterotrophic absorbers that digest food outside the body and absorb it, and animals are heterotrophic ingesters that take food into the body. These differences helped separate Plantae, Fungi, and Animalia. A is wrong because nutrition was not merely a minor feature; it was one of the important bases of the system. C is wrong because the criterion was explicitly accepted in the five-kingdom scheme. D is wrong because nutrition modes occur in many groups, not only animals. Memory cue: plant makes, fungus absorbs, animal ingests.