Three letters are dictated to three persons and an envelope is addressed to each of them,the letters are inserted into the envelopes at random so that each envelope contains exactly one letter.Find the probability that at least one letter is in its proper envelope.

Question

$\begin{array}{1 1}(A)\;\large\frac{2}{3}\\(B)\;\large\frac{5}{3}\\(C)\;\large\frac{7}{3}\\(D)\;\text{None of these}\end{array} $