Which of the following is absent in prokaryotes?

Bayer's process is used for the purification of Bauxite containing which of the following as a major impurity?

$A$ magnet freely suspended in a vibration magnetometer makes $40$ oscillations per minute at place $A$ and $20$ oscillations per minute at a place $B$. If the horizontal component of earth's magnetic field at $A$ is $36 \times 10^{-6} ~T$,then its value at $B$ is

$\sqrt[4]{17 + 12\sqrt{2}} = $

$A$ particle $P$ is moving in a circle of radius $a$ with a uniform speed $v$. $C$ is the centre of the circle and $AB$ is a diameter. When passing through $B$,the angular velocity of $P$ about $A$ and $C$ are in the ratio:

Boric acid is $NOT$ used in which of the following?