Which of the following metals belong to the same group in the periodic table?

$A$ man running round a race-course notes that the sum of the distances of two flag-posts from him is always $10 \ m$ and the distance between the flag-posts is $8 \ m$. The area of the path he encloses in square metres is (in $\pi$)

If the change in the value of $g$ at a height $h$ above the surface of the earth is the same as at a depth $x$ below it,then (both $x$ and $h$ being much smaller than the radius of the earth)

The radiant energy from the sun incident normally at the surface of the earth is $20 \ kcal/m^2-min$. What would have been the radiant energy incident normally on the earth if the sun had a temperature twice of the present one? (in $kcal/m^2-min$)

$A$ circle $C_1$ of radius $2$ touches both $x$-axis and $y$-axis. Another circle $C_2$ whose radius is greater than $2$ touches circle $C_1$ and both the axes. Then the radius of circle $C_2$ is-

The electrons,identified by quantum numbers $n$ and $l,$ $(i)$ $n = 4, l = 1$ $(ii)$ $n = 4, l = 0$ $(iii)$ $n = 3, l = 2$ $(iv)$ $n = 3, l = 1$ can be placed in order of increasing energy,from the lowest to highest,as