JBL EMT Complete Practice Exam 2025

Platelets, also known as thrombocytes, are small fragments of specialized cells that play a key role in the formation of blood clots to stop bleeding or repair damaged blood vessels. They do this by forming a sticky plug at the site of injury and releasing chemicals that promote blood clotting.

Option B is the correct answer because platelets are primarily responsible for the initial formation of a blood clot.

Option A is incorrect because defense against invading organisms is the function of white blood cells.

Option C is incorrect because the transport of waste materials is the function of red blood cells.

Option D is incorrect because the transport of oxygen and nutrients is the function of red blood cells, while platelets do not have this function.