Which of the following cells are infected in a person suffering from $AIDS$?
$CD_{4}$ receptor cells
$CD_{8}$ receptor cells
Killer $T$ cells
Germ cells
On which day, world population touched $5 ^{th}$ billion?
$A$ birth control implant having six small, plastic cylinders and with the effective period much longer upto $5$ years is
The centre of $WHO$ is at
The least densely populated state of India is
Distribution of population on earth is