Consider the following statements.
AIDS -is transmitted

Correct Option (b):

Acquired Immunodeficiency Syndrome (AIDS) is caused by the Human Immunodeficiency Virus (HIV). The primary modes of HIV transmission are:

• Sexual intercourse: Through unprotected sexual contact with an infected individual.
• Blood transfusion: Via transfusion of contaminated blood or blood products, or sharing of contaminated needles and syringes.
• Across the placenta: From an infected mother to her child during pregnancy, childbirth, or breastfeeding (known as vertical or mother-to-child transmission).

Therefore, statements 1, 2, and 4 correctly describe modes of HIV transmission.

Incorrect Options:

Statement 3 is incorrect. HIV is not transmitted by mosquitoes or other blood-sucking insects. The virus does not replicate or survive within these insects, thus they cannot act as biological vectors for HIV transmission. Options (a), (c), and (d) are incorrect because they include statement 3.