SAT Biology Subject Test Practice Questions

Answer: D, Platelets. Platelets are recruited to sites of injure and regulate the processes that lead to the formation of blood clots, or coagulation.

Key Takeaway: Platelets are irregular shaped cells that are unique in that they do not contain a nucleus. It is essential to health that the number of platelets is maintained at a proper level. A deficiency in platelets can lead to bleeding disorders, and too many platelets can result in aberrant clot formation within blood vessels, leading to stroke or heart attack.