Step 1: Understanding the Problem:
Sexually Transmitted Infections (STIs) are diseases transmitted primarily through sexual contact. Their curability heavily depends on the nature of the causative pathogen (bacterial vs. viral).
Step 2: Approach and Formula:
Categorize the common sexually transmitted infections into curable (usually bacterial or protozoan) and currently incurable (specific severe viral infections).
Step 3: Detailed Explanation:
Medical texts emphasize that while many STIs are completely curable if detected early and treated adequately (e.g., Syphilis, Gonorrhoea, Chlamydiasis, Trichomoniasis), there are distinct viral exceptions.
Specifically, three viral infections are considered completely incurable with current medical science:
1. Hepatitis-B (caused by HBV)
2. Genital herpes (caused by HSV)
3. HIV infection (which leads to AIDS)
Looking at the options provided, Option (D) lists both "AIDS" and "Genital herpes", forming the correct pair of incurable diseases.
Step 4: Final Answer:
AIDS and Genital herpes are not completely curable.