Answer:
A is the correct answer 
Explanation:
the existed about 3.8to 4.0 billion years ago
 
        
             
        
        
        
Answer:
the awnser is A river basin
Explanation:
because I'm smart just trust me m8
 
        
             
        
        
        
<span>In response to a body temperature above the set point, two effector responses in mammals could be sweating and panting. 
</span><span>Negative feedback stimulate activities of effectors (including sweat glands) that lower the temperature.</span>
        
                    
             
        
        
        
Answer:
The answer is "species richness." 
Explanation:
It is a term that relates to the amount of species in a environment, and also has to do with measuring the diversity of a species in a community.