T-tubules or transverse tubules are a part of the skeletal and cardiac muscle membrane systems. They are the cell membrane extensions that can penetrate into the center of those muscles.
It contains a large amount of on channels, transporters, and pumps. It allows the transmission of the action potential, frequently. T-tubules also regulates the cellular calcium concentration.
Your answer would be A. The earth element stays in the same area of the lithosphere, hydrosphere, or atmosphere where they originated when the earth was formed.
