Given the task definition and input, reply with output. In this task, you need to provide the correct option for a given problem on probability from the provided options.

Problem: 3 houses are available in a new flat . 3 persons apply for the houses . each applies for 1 house without consulting others . the probability that all the 3 apply for the same house is ? 
Options: a ) 1 / 7 , b ) 1 / 9 , c ) 2 / 7 , d ) 3 / 7 , e ) 2 / 9

b