These entities form lines of Zahn when they appear in the heart or the aorta, because they have alternating layers of platelets made of fibrin. If one of these entities becomes free-floating, it is referred to as an embolus, and causes of these entities can include heart arrhythmia and long periods of inactivity. Treatments for these entities include heparin and warfarin, both of which can inhibit their formation and growth in the body. For 10 points, name these entities, which are helpful in coagulation but can lead to harmful effects like thrombosis.
a) Platelets
b) White Blood Cells
c) Red Blood Cells
d) Blood Clots