- A Each couplet relies on one contrasting feature, so a missing structure misleads that step
- B Dichotomous keys work for animal specimens, not plant ones under normal conditions as generally observed
- C The key lists every related species no matter which character is chosen under usual circumstances
- D Dichotomous keys are built without using morphological characters in typical laboratory settings
Correct answer: A. Each couplet relies on one contrasting feature, so a missing structure misleads that step
Explanation: Since each couplet in a dichotomous key depends on observing a particular contrasting character, a damaged specimen lacking that structure can lead the user down the wrong branch.
Concept context
Biodiversity, taxonomy, binomial nomenclature, the taxonomic hierarchy, and taxonomic aids like herbaria and botanical gardens. The foundational first chapter of NCERT Biology.