Which one of the following is the first step in taxonomy?

Which of the following vessels in a rabbit starts with capillaries and ends in capillaries?

If $u = x y^2 \tan^{-1}\left(\frac{y}{x}\right)$, then $x \frac{\partial u}{\partial x} + y \frac{\partial u}{\partial y}$ is equal to

Which of the following compounds is optically active?

$A$ thin rod of length $L$ is bent to form a semicircle. The mass of the rod is $M$. What will be the gravitational potential at the centre of the circle?

$A$ 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: