The correct answer is option 1: Retrovirus. AIDS, which stands for Acquired Immunodeficiency Syndrome, is caused by the Human Immunodeficiency Virus (HIV). HIV is a type of retrovirus, meaning it has RNA as its genetic material instead of DNA. Retroviruses are unique because they have the ability to convert their RNA into DNA using a special enzyme called reverse transcriptase. This allows the virus to integrate its genetic material into the DNA of the host cell it infects.

Option 2: Lente virus is not the correct answer. Lente viruses are a type of virus that can cause slow and persistent infections, but they are not specifically associated with HIV or AIDS.

Option 3: Arbovirus stands for arthropod-borne virus. While there are arboviruses that can cause diseases such as dengue fever or Zika virus, HIV is not an arbovirus.

Option 4: Immune virus is not a specific term used to describe a type of virus. Although HIV does directly impact the immune system, it is not referred to as an "immune virus."

In summary, HIV, the virus that causes AIDS, is classified as a retrovirus because it has RNA as its genetic material