A dichotomous key is a tool that helps the user to determine the identity of items in the natural world, such as trees, wildflowers, mammals, reptiles, rocks, and fish. 
        
             
        
        
        
Answer:
A balanced equation is an equation for a chemical reaction in which the number of atoms for each element in the reaction and the total charge are the same for both the reactants and the products. In other words, the mass and the charge are balanced on both sides of the reaction.
Explanation:
 
        
                    
             
        
        
        
Answer:
Because it contains two different sex chromosomes
Explanation:
Man in its genome contains two sex chromosomes, X and Y, while woman contains two X chromosomes.
In order to be a carrier of a sex-linked trait, a person should have one copy (one allele) of a certain trait. For example, if a female has one X chromosome with mutation (e.g. disease carrying) and one normal X chromosome, she is carrier for the disease. But, on the other hand if a male has one X chromosome with mutation he will develop that disease.