10 books are placed at random in a shelf. The probability that a pair of books will always be together is ? Choose the correct choice from the following.
A) 1/7
B) 2/5
C) 1/5
D) 1/3
E) 3/5
10 books can be rearranged in 10! ways consider the two books taken as a pair then number of favourable ways of getting these two books together is 9! 2!   Required probability   = 1/5   Answer:1/5
<result>C</result>
10 books are placed at random in a shelf. The probability that a pair of books will always be together is ?