21.
Seven boys B1, B2, B3, B4, B5, B6, and B7 are sitting in a row facing towards south (not necessarily in the same order). B7 is not the neighbour of B1. B3 is to the immediate right of B4 but is not the neighbour of B5. B2 sits at one of the extreme ends and is the neighbour of B4. Only two boys sit between B1 and B5.
Which of the following position of B6 is correct?