With reference to taxonomical aids, correct statements are A. Each statement in the key is called a couplet. B. Herbarium is a storehouse of collected plant and animal specimens. C. Separate taxonomic keys are required for each taxonomic category. D. Keys are used for identification purposes.

Step-by-step solution

Key is a type of taxonomical aid that is used for the identification of both plants and animals based on the similarities and dissimilarities. Usually, for each taxonomic category like species, genus, family, etc., separate taxonomic keys are required. Each statement in the key is called Lead while a pair of keys based on contrasting characters is called a couplet. The herbarium is a store house of collected plant specimens that are dried, pressed and preserved on sheets.