Which of the following graphs is in accordance with the Maxwell distribution of molecular velocities and its dependence on temperature? 

Fraction of molecules are plotted against velocity of molecules, according to Maxwell-Boltzmann distribution law. The velocity corresponding to the points $\mathrm{X}, \mathrm{Y}$ and $\mathrm{Z}$ are:

Here,

 ${\mathrm{v}}_{\mathrm{mp}}=$ most probable velocity.
${\mathrm{v}}_{\mathrm{av}}=$ average velocity.
$v_{\mathrm{rms}}=$ root mean square velocity.