I believe the answer is C
Manipulation of the independent variable should change the dependent variable, the value of which "depends" on the independent variable's change in value.
The products will be 
<h3>Chemical reactions</h3>
Zn is higher than hydrogen in the reactivity series. Thus, it will be able to displace hydrogen from the acid.
The equation of the reaction becomes: 
Hydrogen gas is released as a result. In fact, it is one of the ways of preparing hydrogen gas in the laboratory.
More on chemical reactivity can be found here: brainly.com/question/9621716
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The answer would be Gravity.