Among the following series of transition metal ions,the one where all metal ions have $3d^2$ electronic configuration is

$A$ healthy person eats the following diet: $5 \ gm$ raw sugar,$4 \ gm$ albumin,$10 \ gm$ pure buffalo ghee adulterated with $2 \ gm$ vegetable ghee (hydrogenated vegetable oil) and $5 \ gm$ lignin. How many calories is he likely to get?

The centre of a circle is $(2, -3)$ and the circumference is $10\pi$. Then the equation of the circle is

$A$ line segment $l$ of length $a \ cm$ is rotated about a vertical line $L$ keeping the line $l$ in one of the following three positions: $(I)$ $l$ is parallel to $L$ and is at a distance of $r \ cm$ from $L$,$(II)$ $l$ is perpendicular to $L$ and its mid-point is at a distance $r \ cm$ from $L$,$(III)$ $l$ and $L$ are in the same plane and $l$ is inclined to $L$ at an angle $30^{\circ}$ with its mid-point at a distance $r \ cm$ from $L$. Let $A_1, A_2, A_3$ be the areas so generated. If $r > (a / 2)$,then

Fog is a colloidal solution of

In a two-slit experiment with monochromatic light,fringes are obtained on a screen placed at some distance from the slits. If the screen is moved by $5 \times 10^{-2} \ m$ towards the slits,the change in fringe width is $3 \times 10^{-5} \ m$. If the separation between the slits is $10^{-3} \ m$,the wavelength of light used is ......... $\mathring{A}$.