The spread of $AIDS$ occurs through.........

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.

In which condition does the $CD_4$ count in the blood fall below $200 \times 10^{6}$ cells/$L$?

Which option correctly identifies $p, q, r$ and $s$ in the given figure of the $HIV$ virus?

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

Which of the following cells are infected in a person suffering from $AIDS$?