What does '$A$' represent in the given figure?

Identify the correct sequence for the mechanism of $HIV$ infection:
$1.$ Viral $RNA$ replicates to form viral $DNA$ with the help of reverse transcriptase.
$2.$ The progeny viruses released in the blood attack other $T_H$ cells and destroy them.
$3.$ Viral $DNA$ gets incorporated into the host cell's $DNA$ and produces virus particles.
$4.$ Virus enters into macrophages.

What is the nucleic acid present in $HIV$?

$HIV$ decreases the natural immunity of the body by:

Which one of the following statements is correct with respect to $AIDS$?

Immune deficiency syndrome in humans could develop as a consequence of