Final answer:
Proscar, the brand name for finasteride, is the medication that is a 5 Alpha Reductase Inhibitor used to treat benign prostatic hyperplasia (BPH). It works by inhibiting the enzyme that converts testosterone into the hormone that enlarges the prostate.
Step-by-step explanation:
The medication classified as a 5 Alpha Reductase Inhibitor and used as a Benign Prostate Hyperplasia Agent is D) Proscar. Proscar is the brand name for finasteride, which is specifically designed to treat benign prostatic hyperplasia (BPH) by inhibiting the enzyme 5-alpha reductase. This enzyme converts testosterone into dihydrotestosterone (DHT), a hormone that can cause the prostate to enlarge. By reducing the production of DHT, finasteride helps to shrink the prostate and relieve the symptoms associated with BPH.