Sterile needles prevent disease transmission (eliminates (a)). STIs are infectious microbial diseases, not inherited genetic disorders (eliminates (e)). Blood transfusion (b) and vertical transmission from mother to foetus (c) are canonical transmission routes for STIs like Hepatitis-B and HIV. Option (3) is the only valid choice!
1 Evaluate (a): "Using sterile needles" is a prophylactic barrier that PREVENTS infection. Discard options with (a) -> Eliminates Options (1) and (4).
2 Evaluate (e): "Inheritance" refers to Mendelian genetic transmission, whereas STIs are acquired infectious diseases caused by microbes.
3 Evaluate (b) and (c): Blood transfusion from infected persons and vertical transmission (mother to foetus) are well-established non-sexual transmission routes of STIs (Hepatitis B, HIV, Syphilis).
4 Conclude (b) and (c) only -> Option (3).
🛡️ Why You Can 100% Trust This Shortcut: NCERT Biology · Reproductive Health (Sexually Transmitted Infections: Some of these infections like hepatitis-B and HIV can also be transmitted by sharing of injection needles, surgical instruments, etc., with infected persons, transfusion of blood, or from an infected mother to the foetus).