The elements A, B, C, D, and E have atomic numbers 9, 11, 17, 12 and 13 respectively. Which pair of elements belongs to the same group?
The all the above mentioned atomic numbers belong to 2nd and 3rd groups which have a difference of 8 between them so the numbers which have a difference of 8 is ‘9’ and ‘17’. So, the correct option is (c).