<span><em>Density</em>-dependent <em>factors</em> operate only when the population <em>density</em> reaches a certain level. </span>
The answer is A.) The ratio of thier masses is always the same
Id say d because it releases hydrogen and on the other hand a base receives it
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Answer:

Explanation:
The mass of the man can be found by using the formula

f is the force
a is the acceleration
From the question we have

We have the final answer as
<h3>50 kg</h3>
Hope this helps you