Which is the best method to conserve the wild relatives of plants?

$\operatorname{sech}^{-1}(\sin \theta)$ is equal to

If the curves $\frac{x^2}{a^2}+\frac{y^2}{b^2}=1$ and $\frac{x^2}{25}+\frac{y^2}{16}=1$ cut each other orthogonally,then $a^2-b^2$ equals to

Assertion : Free electrons always keep on moving in a conductor even then no magnetic force acts on them in a magnetic field unless a current is passed through it.
Reason : The average velocity of free electrons is zero.

The $pH$ of water is $7$. When a substance $Y$ is dissolved in water,the $pH$ becomes $13$. The substance $Y$ is a salt of

The correct stability order for $N_2$ and its given ions is