Which of the following are true about the taxonomical aid ‘key’?
A. Keys are based on the similarities and dissimilarities.  
B. Key is analytical in nature.  
C. Keys are based on the contrasting characters in pair, called couplet.  
D. Same key can be used for all taxonomic categories.  
E. Each statement in the key is called lead.  
Choose the most appropriate answer from the options given below. 

The correct answer is A, B, C and E only.

A. Keys are based on similarities and dissimilarities. Taxonomic keys are tools used by taxonomists to identify
and classify organisms based on their similarities and dissimilarities in various characteristics or traits.

B. Key is analytical in nature.

C. Keys are based on contrasting characters in pairs, called couplet. Each step or statement in a taxonomic
key presents a pair of contrasting characteristics that helps the user choose between two options to proceed
further in the identification process.

D. Same key cannot be used for all taxonomic categories. Different taxonomic keys are used for different
taxonomic categories.

E. Each statement or step in a taxonomic key is called a lead, and it presents the contrasting pair of characters to guide the user to the next appropriate step for identification.