I need help with this physics problem..?

[Michael H]

A sample of an ideal gas is in a tank of constant volume. The sample absorbs heat energy so that its temperature changes from 300 K to 600 K. If v1 is the average speed of the gas and molecules before the absorption of heat and v2 is their average speed, after the absorption of heat, what is the ratio of v2 / v1?

a) 1/2
b) 1
c) square root of 2
d) 2
e) 4

Thanks!