The length of the tangent drawn to the circle $x^2+y^2-2x+4y-11=0$ from the point $(1,3)$ is:

Match the following columns.

Column-$I$	Column-$II$
$A.$ $500$ million years ago	$1.$ Invertebrates
$B.$ $350$ million years ago	$2.$ Jawless fishes
$C.$ $320$ million years ago	$3.$ Sea weeds and few plants

Seven white balls and three black balls are randomly arranged in a row. The probability that no two black balls are placed adjacently is

The Cartesian form of the polar equation $\theta = \tan^{-1} 2$ is

What is the decreasing order of reactivity of $HX$ in the given reaction: $ROH + HX \rightarrow RX + H_2O$?

$A$ transition metal $M$ forms a volatile chloride with a vapor density of $94.8$. If it contains $74.75\%$ chlorine,what is the formula of the metal chloride?