The graph which represents the variation of mean kinetic energy of molecules with temperature t^oC is : 

Mean KE of gas molecule : \(E = \frac{3}{2}kT\)

\(E = \frac{3}{2}k(t + 273)\)

... where T is temperature in kelvin and t is in centigrade.

\(E = \frac{3}{2}kt + \frac{3}{2}*273 k\)

... where k = Boltzmann's constant.

By comparing this equation with standard equation of straight line : y = mx + c

We get : m = \(\frac{3}{2}k\) and c = \(\frac{3}{2}*273 k\). 

So, the graph between E and will be straight line with positive intercept on E-axis and positive slope with t-axis.