An experiment or survey must be controlled in order to receive accurate results.
In an experimental group, the independent variable is changed. But in the control group, the independent variable stays the same.
        
                    
             
        
        
        
 Answer:The placement of fossils throughout the sruface layers of earth
Explanation: 
 
        
                    
             
        
        
        
Incubation stage is the stage where the prepares and begins a full on assault of your body.
        
             
        
        
        
<span>During a micro-sleep, you are likely to have a blank stare, sudden shake of the body, head snapping and you are not able to recall a last minute.
The duration of micro-sleep are from 1 second to 30 second.
It can happen to anyone and at any time of the day. there are many reason of micro-sleep and it is said to be dangerous, especially when you are driving.
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B THEY RELEASED CARBON DIOXIDE, WHICH  EVOLVING ANIMALS NEEDED.