Answer: I belevs it is d hope this helps
Explanation:
A. Community.
This is because a community contains living this, and biotic means living.
<span>In the "all or none" law of muscle contraction, it states that when the stimulus applied exceeds threshold then the the nerve sending signals to a few muscle fibers will give a complete response; contraction. Graded response is dependent on how many motor units have been recruited. The more motor units, the greater the force in the contraction.</span>
