Answer:
all of the above
Explanation:
because power plant are the ones that cause pollution,it can also destroy ecosystems for animals,and it cant be built anywhere.
The answer for this question is Control Variable because it doesn’t change throughout the experiment.
We use the equation of motion for vertical component,

Here,
is displacement of bullet,
is vertical initial velocity of bullet which is equal to zero because bullet was fired horizontally, and t is time of flight.
Therefore,

Given, 
Substituting the values, we get time of flight

The centripetal force needed to keep earth in orbit is gravity.
An object that could be considered as negatively charged would be when it has an excess of an electron in its atom. However, when it loses an electron, it could go back to its stable state which is "uncharged" or when there is an excess proton, it could be a positively charged object.