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

5FU
15LS
9IT
17OR

The answer is A. 5FU.

The series is a simple addition of 4 to the previous number, except for 5FU. The correct sequence should be 1CC, 5FU, 9IT, 13LU, 17OR.

1CC + 4 = 5FU
5FU + 4 = 9IT
9IT + 4 = 13LU
13LU + 4 = 17OR

Therefore, 5FU is the odd one out.