Which of the following series of transition metal ions all have a $3d^2$ electronic configuration?

The incentre of the triangle with vertices $(1, \sqrt{3})$,$(0, 0)$ and $(2, 0)$ is

Which one of the following does not correctly represent the order of property indicated against it?

$1\, kg$ of a diatomic gas is at a pressure of $8 \times 10^4\, N/m^2$. The density of the gas is $4\, kg/m^3$. What is the energy of the gas due to its thermal motion?

The focal length of an equi-convex lens is greater than the radius of curvature of any of the surfaces. Then the refractive index of the material of the lens is

The output characteristics of an $n-p-n$ transistor represent,($I_C=$ collector current,$V_{C E}=$ potential difference between collector and emitter,$I_B=$ base current,$V_{B B}=$ voltage given to base,$V_{B E}=$ the potential difference between base and emitter)