After the typist writes 12 letters and addresses 12 envelopes, she inserts the letters randomly into the envelopes (1 letter per envelope). What is the probability that exactly 1 letter is inserted in an improper envelope?
A
0
B
12/212
C
11/12
D
1/12
Correct Option - A
Explaination
If all the other 11 letters are inserted in the correct envelopes, the 12th one should also be in the correct envelope. Hence, the probability is zero.