Final answer:
Finasteride is the 5-alpha-reductase inhibitor that blocks conversion of testosterone to dihydrotestosterone, reducing the size of the prostate.
Step-by-step explanation:
The 5-alpha-reductase inhibitor that blocks conversion of testosterone to dihydrotestosterone, reducing the size of the prostate is Finasteride (option c).
Finasteride is commonly used to treat male pattern hair loss by inhibiting the enzyme 5-alpha-reductase, which converts testosterone to dihydrotestosterone. By reducing dihydrotestosterone levels, Finasteride can shrink the prostate and improve hair loss in men. However, it may cause side effects such as gynecomastia, erectile dysfunction, and depression.
The other options, Terazosin (a), Doxazosin (b), and Prazosin (d), are alpha-blocker medications used to treat high blood pressure and urinary symptoms associated with an enlarged prostate, but they do not inhibit the conversion of testosterone to dihydrotestosterone.