Answer:
Option D, a blood clot attached to a blood vessel
Explanation:
The blood is composed of different types of cells, aptly and collectively referred to as the blood products. Amongst these products are the red blood cell fragments, known as thrombocytes (sometimes called platelets), that aid the process of wound healing when blood vessel damage occurs.
The thrombocytes group together at the site of the damage and form a clump of cells to help with the healing and repair process; this clump of cells is known as a thrombus, which are sometimes known as platelet plugs, but colloquially, they are called blood clots.
A thrombus remains attached to the vessel wall until broken during normal bodily processes like fibrinolysis. If it becomes detached and circulates, it is no longer called a thrombus; rather, it is now termed an embolus.
Therefore, option D, best described a thrombus: a blood clot attached to a blood vessel