Answer:
because it can change in an instant
Explanation:
 
        
                    
             
        
        
        
D, you have the right answer. Kalanchoe plants produce asexually
        
                    
             
        
        
        
Answer:
Positive natural selection. 
Explanation:
The positive natural selection is a type of natural selection that increases the frequency of an allele or trait when it is advantageous for the population. What happened in the example is that the mouth with the slight change in  morphology (trait)  was more advantageous for the population in the south in relation to the  ancestral morphology  (still preserved in the population in the north), and therefore its frequency increased. This, in turn, is due to the fact that the food (prey) is not the same in the two habitats (north and south).  The specific prey in the south,  caused the new morphology to be selected, (increasing the frequency of individuals with the new mouth),  becasue probably that trait allows the trouts in the south to hunt more effectively.
 
        
             
        
        
        
Answer: Chlorine
Explanation:
An independent variable can be define as changable variable, which can be used to determine it's impact over the other variable(s) in the experiment. Dependent variable cannot be changed manually instead changes occur in the independent variable is because of impact of independent variable. 
In this experiment, chlorine is the independent variable. The effect of which can be observed on the hair color, which is a dependent variable.
 
        
             
        
        
        
The answer is Catecholamine. It is any of a class of aromatic amines that includes a number of neurotransmitters such as epinephrine and dopamine. The adrenergic receptors are a class of G protein-coupled receptors that are targets of the catecholamines, especially norepinephrine (noradrenaline) and epinephrine (adrenaline). These three - catecholamine, peptide hormones and eicosanoids acts as extracellular membrane receptors which means that these receptors are embedded in the membranes of cells. They act in cell signaling by receiving (binding to) extracellular molecules.