A because look at the y axis and its by 10's so add the extra numbers in it and its should b a because look at the first point I am sorry if my explanation is not clear but I hoped I helped:D
root means square velocity of one mole of a monoatomic gas having molar mas*s m(M) is Urms. The relation between average kinetic energy (e)of the gas and Urms is Urms=M2E
