Answer:
The correct answer will be option-C
Explanation:
The rhythm of the heartbeat is controlled by the pacemaker of the heart called the sino-atrial node.
The SA node generates action potentials which trigger the contraction and relaxation of the atrium and ventricles. The membrane potential generation initiates by the depolarization of the cell membrane when the L type of Ca⁺² ions opens up and calcium ions enter the cell.
This depolarizes the cell until the potential threshold is reached which lies between the -40 and -30 mV.
Thus, Option-C is the correct answer.
They have their tentacles which house cells called<span> cnidocytes.</span>
The answer is A) Carbon
Hope this helps.
<span>This theory is called punctuated equilibrium. In this theory it is explained that there are very long periods of no change at all to a species, yet there are also bursts of evolutionary change interspersed within the time period. The period of remaining the same throughout time (most of the time) is called stasis, and is present within this theory of punctuated equilibrium.</span>
