The variable that researchers manipulate is the independent variable.
The reason for this is because in experiments different manipulations are often introduced. The sole purpose of these manipulations is to see whether they will affect our independent variable and if they will change its value. 
        
                    
             
        
        
        
Where are the following choices
        
                    
             
        
        
        
Answer:
Answer: The correct option is, It is a line joining the points whose x and y coordinates add up to 4.Step-by-step explanation:The given equation
Explanation:
Since x=4 is a vertical line, there is no y-intercept and the slope is undefined.
 
        
             
        
        
        
Think of a sponge. The more porous (ability to absorb, what happens to that sponge?) it is more permeable (ability to move). A
        
             
        
        
        
Answer:
The researchers were unable to grow the microbe in the laboratory BECAUSE THE PREVAILING ROOM TEMPERATURE IN THE LABORATORY IS UNSUITABLE FOR THE GROWTH OF THE MICROBE.
Explanation:
Microbes that grow near deep sea thermal vent usually have the ability to exist in environment that have abnormally high temperatures. In order for a researcher to grow such microbes in the laboratory, he must be able to reproduce the high temperature that is found in the natural habitat of the micro organisms. Growing the microbes in the laboratory at room temperature will be unsuccessful because the microbes can not survive at that temperature.