Out of molar entropy $(I)$,specific volume $(II)$,heat capacity $(III)$,volume $(IV)$,which are extensive properties?

$A$ function $y = f(x)$ is given by $x = \frac{1}{1 + t^2}$ and $y = \frac{1}{t(1 + t^2)}$ for all $t > 0$. Then $f$ is:

Which of the following is not used in Friedel-Crafts reaction?

Most of the endangered species are the victims of

$A$ particle of mass $M$ is situated at the centre of a spherical shell of mass $M$ and radius $a$. The gravitational potential at a point situated at a distance of $\frac{a}{2}$ from the centre will be:

Which of the following substances is used in smoke screens?