A three stage telephone switching structure is to have 128 input and 128 output terminals. There are 16 first stage and 16 third stage matrices. To avoid blocking the number of intermediate paths required is

Q. A three stage telephone switching structure is to have 128 input and 128 output terminals. There are 16 first stage and 16 third stage matrices. To avoid blocking the number of intermediate paths required is

A.            16

B.            15

C.            8

D.            1

Answer: 15