Answer:
Option A, thrombus
Step-by-step explanation:
A blood clot that forms abnormally in the blood vessel is known as a thrombus. The condition surrounding this phenomenon is called thrombosis, which is option A.
These abnormal blood clots are particularly dangerous because they can become embedded within vessels that are too small for the clot to pass through, thereby causing edema (or swelling), altering the perfusion of oxygen to tissues, and or interfering with the ability of blood to travel to the heart, lungs, and brain. When a thrombus travels and is lodged within the vasculature, it is then called an embolus, and the occlusion it creates is the condition called embolism.
An aneurysm is an outward bulging of a blood vessel that, if it weakens, can rupture and creating internal bleeding that becomes an medical emergency, especially if it occurs in the brain or in the abdominal aorta. That outpouring of blood from this burst blood vessel would be known as a hemorrhage -- it can range from a mild as a bruise or major blood loss.
To return back to the answer, an abnormal blood clot forming within the circulatory system is called a thrombus, and the condition is thrombosis, option A.