__________ is a choice between two contradictory statements resulting in the acceptance of one and the rejection of the other.
A. Manual
B. Monograph
C. Taxonomic key
D. Herbarium

Hint: A solitary pair of contrary statements is known as a couplet and every announcement of a couplet is named as a lead. By settling on the right decision at each level, one can in the long run show up at the name of the obscure plant. Since identification and terminology are essential for characterization; the initial step is identification trailed by classification and then order.

Complete answer:
A key is a gadget, which when appropriately developed and utilized, empowers a client to distinguish a living being. Keys are gadgets comprising a progression of differentiating or conflicting explanations or suggestions requiring the identifier to settle on correlations and choices dependent on statements in the key as identified with the material to be recognized.
Along these lines, a taxonomic key is a gadget for rapidly and effectively recognizing to which species an obscure plant has a place.
The key comprises a progression of choices, because of the view highlights of the plant specimen. It gives a decision between two contradicting statements bringing about the acknowledgment of one and the dismissal of the other.

Hence, the correct answer is option (C).

Additional information:
A manual is a handbook giving total aggregated data about a specific zone with all the families, genera, species, and keys for their distinguishing proof.
A monograph is an extensive methodical investigation of a specific scientific categorization. Monographs attempt to audit the real factors about a scientific categorization, species depictions.
An herbarium is a safeguarded reference assortment of plants and is imperative to a wide range of zones of science. It goes about as a wellspring of data about plants.

Note: Taxonomic keys are gadgets consisting of a progression of differentiating or contradictory statements or suggestions requiring the identifier to settle on correlations and choices dependent on articulations in the key as identified with the material to be recognized. It is a taxonomic guide utilized for the ID of plants and creatures dependent on the similarities and dissimilarities. The keys depend on differentiating characters for the most part in a pair called a couplet.