probability question

[theben]

Heres the Q, not my own

Tom, Dick and Harry are in prison. One of them is scheduled to die in the morning, and the other two will be set free. Their guard knows which one will die, but none of the prisoners does. The guard is under strict instructions not to divulge the identity of the doomed man. Tom is desperate for any information beyond the fact that his odds of death are one in three. He begs the guard to throw him an informational bone. Finally, to shut him up, the guard agrees to reveal only the following: the name of one of Tom's fellow prisoners who will be set free rather than killed. The guard then says that Dick will be set free. After the guard's revelation, what is the probability that Tom will be killed?

a. 1/3
b. 1/2
c. 2/3
d. none of these