If a digit is chosen at random from the digits 1, 2, 3, 4, 5, 6, 7, 8, 9; then the probability that this digit is an odd prime number is:

If a digit is chosen at random from the digits $\displaystyle 1$, $\displaystyle 2$, $\displaystyle 3$, $\displaystyle 4$, $\displaystyle 5$, $\displaystyle 6$, $\displaystyle 7$, $\displaystyle 8$, $\displaystyle 9$; then the probability that this digit is an odd prime number is :