Correct Answer - B
Since lines are more than telegrams, `.^(N)C_(M)` are those lines where telegrams will be sent.
So, number of favourable cases = `.^(N)C_(M) xx M!`
Total number of cases = `N^(M)`
[As first telegram can go in any one of n lines]
So, required probability = `(.^(N)C_(M)xxM!)/(N^(M))`