The term "independent variable" means precisely what it sounds like. It is a variable that is independent of the other factors you are attempting to assess.
<h3>What is independent and Dependent variable?</h3>
- Dependent variables are so named because their values are explored in an experiment under the assumption or requirement that they are dependent, by some law or rule, on the values of other variables.
- The group that does not get the new medication being investigated in a clinical trial. This group is compared to the group that receives the new treatment to see if the new treatment is effective.
- Assume you want to put a new ADHD medicine to the test. One group would be given the new medication, while the other would be given a tablet that looked precisely like the one given to the others, but it would be a placebo. 
- The control group would be the group that receives the placebo. A control group is the "untreated" group with which an experimental group (or treatment group) is contrasted in experimental designs. 
- It is made up of research units that did not receive the treatment whose effect is being studied.
To learn more about independent variable, refer to:
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Answer; 
A bottleneck effect
Explanation; 
When only a few individuals survive unfavorable times, thereby losing the majority of genotypes in the next generation, it is called a bottleneck effect. 
It occurs when there is a disaster of some sort that reduces a population to a small handful, which rarely represents the actual genetic makeup of the initial population.
 
        
             
        
        
        
D: Surface-water runoff from rain
        
                    
             
        
        
        
Answer:
More acidic and carbon dioxide 
Explanation:
Cause I took the test