Which one of the following statements is correct regarding sexually transmitted diseases (STDs)?

The chances of a 5-years boy contacting a STD are very little because transmission of HIV-infection generally occurs by (a) sexual contact with infected person, (b) by transfusion of contaminated blood and blood products, (c) by sharing infected needles as in the case of intravenous drug abusers and (d) from infected mother to her child through placenta.A person cannot contact syphilis by sharing milk with one already suffering from the disease.Haemophilia is a sex linked recessive genetic disorder.Genital herpes is an STD. Sickle-cell anaemia is an autosomal recessive genetic disorder.