Which one of the following characteristics of the transition metals is associated with their catalytic activity?

$A$ sound wave passing through an ideal gas at $NTP$ produces a pressure change of $0.001 \text{ dyne}/cm^2$ during adiabatic compression. The corresponding change in temperature $(\gamma = 1.5$ for the gas and atmospheric pressure is $1.013 \times 10^6 \text{ dyne}/cm^2)$ is:

If the eccentricity of a hyperbola is $\sqrt{3}$,then the eccentricity of its conjugate hyperbola is:

Four charges equal to $-Q$ are placed at the four corners of a square and a charge $q$ is at its centre. If the system is in equilibrium,the value of $q$ is:

The period of $\sin ^4 x + \cos ^4 x$ is

The coefficient of $x^n$ in $\frac{1-2x}{e^x}$ is: