Hint:Key is a taxonomical aid for the identification of organisms on the basis of similarities and dissimilarities. It is a simple tool to identify specific objects. They are generally analytical in nature.
Complete Answer: To answer this question, we must know about the taxonomic key. It is a simple tool used to identify an organism. Key consists of a series of contrasting or contradictory statements or propositions required by the identifier to make conclusions based on these statements. It is used for quick and easy identification of species of an unknown plant. Separate taxonomic keys are needed for each taxonomic category like family, genus and species. The contrasting character on which the key is based is called a couplet. It occurs in a pair. Each statement in the couplet is called a lead. By the correct choice at each level, the name of the unknown plant can be derived. Thus the correct answer is (B) “Key” is a taxonomical aid used for the identification of organisms. Each statement in key is called a lead.
Note:The key has many choices which are based on the observed features of the plant specimen. It provides a choice between the two contradictory statements in which one is accepted and the other is rejected. These contradictory statements are known as lead.