For better survival of the human population,which of the following steps is most important?

Reserpine is obtained from ...... .

The value of $k$,if $(1,2)$ and $(k,-1)$ are conjugate points with respect to the ellipse $2x^2 + 3y^2 = 6$ is:

$A$ man of mass $m$ starts falling towards a planet of mass $M$ and radius $R$. As he reaches near to the surface,he realizes that he will pass through a small hole in the planet. As he enters the hole,he sees that the planet is really made of two pieces: a spherical shell of negligible thickness of mass $2M/3$ and a point mass $M/3$ at the centre. What is the change in the force of gravity experienced by the man?

The energy of a photon is calculated by

The volume-temperature graphs of a given mass of an ideal gas at constant pressures are shown below. What is the correct order of pressures?