The Translational K.E. of the molecules of a gas at absolute...

The average translational kinetic energy of a gas molecule is given by $E = \dfrac{3}{2} k_B T$.

This shows that the translational kinetic energy is directly proportional to the absolute temperature of the gas, i.e., $E \propto T$.

To double the translational kinetic energy, the absolute temperature must be doubled.

Therefore, the temperature should be increased to $2T$.

Answer: increasing T to 2 T