The correct option is A 5
Maximum number of spectral lines (N) corresponding to transition from n1=7 to n2=1 are:
N= number of lines emitted =12(n1−n2)(n1−n2+1)
=12(7−1)(7−1+1)
=21
From total spectral lines, lines falling in Balmer series is
five (7→2,6→2,5→2 , 4→2 and 3→2).
Number of transitions in Balmer series =5