Which of the following is not an ore of magnesium?

$A$ fully charged capacitor $C$ with initial charge $q_0$ is connected to a coil of self-inductance $L$ at $t=0$. The time at which the energy is stored equally between the electric and the magnetic field is

Sunflower is primarily cultivated for which of the following?

The electronic configurations of $Eu$ (Atomic No $63$),$Gd$ (Atomic No $64$) and $Tb$ (Atomic No $65$) are

$2 \tanh^{-1} \frac{1}{2}$ is equal to

The number of $5$-digit numbers that are not divisible by $5$ and consist of different odd digits is: