Which among the following is caused by retrovirus ?

AIDS

The correct answer is Option (1) -AIDS

AIDS (Acquired Immunodeficiency Syndrome) is caused by the Human Immunodeficiency Virus (HIV), which is a retrovirus. Retroviruses are a type of virus that uses RNA as their genetic material and reverse transcribe it into DNA once they infect a host cell. HIV attacks the immune system, specifically the CD4+ T cells, leading to a weakened immune response and making the body vulnerable to opportunistic infections.

The other conditions are caused by different types of pathogens:

• Syphilis is caused by the bacterium Treponema pallidum.
• Gonorrhoea is caused by the bacterium Neisseria gonorrhoeae.
• Trichomoniasis is caused by the protozoan Trichomonas vaginalis.

Thus, AIDS is the only disease in the list caused by a retrovirus.