We need blood because it carries oxygen and helps us sustain life. The organ that pushes blood through the body is the heart.
I am pretty sure that if muscle cells failed to function properly the thing that would happen is being revealed by the first option : A. The muscles will not work. I choose this one because as you know muscles are made of muscle tissue and if cells fail it won't functionate at all.
The answer that seems like would best fit this graph would be "(4)Years"
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This I think definitely will help :)