Which platelet-released substance helps additional platelets adhere to the injury site?

1. As platelets collect they release several chemicals from their granules into the plasma. 2. Adenosine diphosphate helps additional platelets to adhere to the injury site. 3. That recruitment reinforces and expands the plug, making the process self-amplifying. 4. Serotonin has a different job, maintaining vasoconstriction. 5. Prostaglandins and phospholipids also maintain vasoconstriction and activate further clotting chemicals. 6. So three of the four are vasoactive or procoagulant, and only adenosine diphosphate recruits more platelets, which is the distinction the question turns on. _Source: OpenStax Anatomy and Physiology (CC BY 4.0), Ch 18 "The Cardiovascular System: Blood", section 18.5 Hemostasis_