Consider the following statements regarding the transmission of AIDS:

1. By sexual intercourse
2. By blood transfusion
3. By mosquitoes and other blood-sucking insects
4. Across the placenta

Of these statements:

A) I, II and III are correct
B) I, II and IV are correct
C) I, III and IV are correct
D) I and III are correct

HIV (the cause of AIDS) is transmitted through sexual contact via infected semen and genital secretions and through direct transfer of infected blood and blood products, so statements I and II are correct [2]. Mother-to-child (vertical) transmission can occur in utero across the placenta, during delivery, or through breast milk, making statement IV correct as well [2]. Conversely, HIV is not spread by mosquitoes or other blood‑sucking insects; insect bites are not a recognized route of HIV transmission, so statement III is incorrect [3]. Therefore the correct combination is I, II and IV.

Sources

1. [1] Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 8: Natural Hazards and Disaster Management > AIDs/HIVs > p. 81
2. [2] https://www.smchealth.org/sites/main/files/file-attachments/kassaye_levy_hiv_trans.pdf
3. [3] https://hivinfo.nih.gov/understanding-hiv/fact-sheets/understanding-hiv-transmission