The catalyst and promoter respectively used in the Haber's process of industrial synthesis of ammonia are

Consider the following standard electrode potentials ($E^o$ in volts) in aqueous solution:

Element	$M^{3+}/M$	$M^{+}/M$
$Al$	$-1.66$	$+0.55$
$Tl$	$+1.26$	$-0.34$

Based on these data,which of the following statements is correct?

The coordinates of the point $P$ on the curve $x=a(\theta+\sin \theta), y=a(1-\cos \theta)$,where the tangent is inclined at an angle $\frac{\pi}{4}$ to the $x$-axis,are

Two particles which are initially at rest,move towards each other under the action of their internal attraction. If their speeds are $v$ and $2v$ at any instant,then the speed of the centre of mass of the system will be

Two rain drops reach the earth with different terminal velocities having ratio $9:4$. Then the ratio of their volumes is

What is the correct order of solubility in water for $He, Ne, Ar, Kr, Xe$?