Something that is invisible that you can not see.
Answer:
The type of liquid in the tub (salt water or vinegar)
Explanation:
<em>The manipulated independent variable in Anita's experiment is </em><em>the type of liquid in the tub. </em>
The independent variable is the controlled or manipulated variable in the course of an experiment. It can also be referred to as the 'cause' variable which has the capacity to produce 'effects' on another variable - the dependent variable.
In this case, the type of liquid the tub is filled (salt water or vinegar) will hypothetically affect the rusting period of the steel. Hence, the dependent variable is the type of liquid the tub is filled while the dependent variable would be the time it takes for the steel to get rusted.
Density, I am pretty sure this is the correct answer.
