Who discovered viroids?

This is the $1^{st}$ and $2^{nd}$ exam question.

$A$ 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:

In which of the following production processes is limestone $(CaCO_3)$ $NOT$ used?

The maximum value of $\sin (\cos (\tan x))$ is

The main objective of the production/use of herbicide-resistant $GM$ crops is to