Final answer:
Aspirin, NSAIDs, and alcohol can all inhibit platelet aggregation and increase bleeding risk, hence the correct answer is d) All of the above.
Step-by-step explanation:
The substance that can inhibit platelet aggregation, posing a high risk of bleeding when used in injections is aspirin. Aspirin inhibits the function of platelets by preventing the formation of thromboxane A2 (TXA2), which is a potent agent for aggregation. This characteristic, coupled with similar effects from NSAIDs and the known properties of alcohol to interfere with coagulation, means that the correct answer is d) All of the above. All these substances can increase bleeding time, hence posing a high risk of bleeding. Aspirin and other NSAIDs, like ibuprofen, work by hindering the synthesis of prostaglandins by inhibiting the cyclooxygenase (COX) enzyme critical in platelet function.