If $|a|=1, |b|=2$ and the angle between $a$ and $b$ is $120^{\circ}$,then ${(a+3b) \times (3a-b)}^2$ is equal to

Which of the following is not true for a species?

$A$ cell is connected between the points $A$ and $C$ of a circular conductor $\text{ABCD}$ of center $O$ with angle $\angle AOC = 60^{\circ}$. If $B_1$ and $B_2$ are the magnitudes of the magnetic fields at $O$ due to the currents in arc $\text{ABC}$ and arc $\text{ADC}$ respectively,the ratio $\frac{B_1}{B_2}$ is

$\frac{1}{1 \cdot 3} + \frac{1}{2 \cdot 5} + \frac{1}{3 \cdot 7} + \frac{1}{4 \cdot 9} + \ldots$ is equal to

In which plant group is the structure shown below found?

Choose the correct option regarding the following complex compounds which follows $(F)$ and does not follow $(NF)$ the Sidgwick $EAN$ rule:
$(I) \ [(Ph_3P)_2PdCl_2]$
$(II) \ [NiBrCl(en)]$
$(III) \ Na_4[Fe(CN)_5NOS]$
$(IV) \ Cr(CO)_3(NO)_2$
$(I) - (II) - (III) - (IV)$