Find the term which does not fit into the series: 1CC, 5FU, 9IT, 15LS, 17OR

Answer: Option B

1st letter :1 + 4 = 5 + 4 = 9 + 4 = 13 + 4 = 17
2nd letter :C + 3 = F + 3 = I + 3 = L + 3 = O
3rd letter :V - 1 = U - 1 = T - 1 = S - 1 = R
Thus, the term 15LS is wrong and must be replaced by 13LS.