Consider the following statements regarding HIV: 1. AIDS is caused by the Human Immuno Deficiency Virus (HIV), a member of a group of viruses called retrovirus. 2. Retroviruses possess an envelope enclosing the RNA genome. 3. HIV infection generally occurs through sexual contact with an infected person. 4. HIV infection spreads by mere touch and physical contact with infected individuals. 5. HIV may be transmitted from an infected mother to her child through placenta. Choose the correct answer.