I think it's D. It shields life forms on the surface from radiation?
Answer:
Answer is Sinoatrial node, SA.
Explanation:
The sinoatrial node, SA, is known to be a group of cells which are found at the top of the heart.
The electrical signal that is initiated by the sinoatrial node bring about or stimulates the atria and then the ventricle of the heart.
It should be noted that, the sinoatrial node are regarded as the pacemaker cells.
Nonselective catheter placement
This can also be placed only into the aorta from any approach. Catheter placed into the arterial vessel and not manipulated to another arterial site. This also refers to the catheter that remains in the accessed vessel or that has made it into the aorta. In contrast to the selective catheter placement which is placed into a branch off the aorta or access the vessel. Each vessel arise from the aorta represents different vascularities.
