Odd Word/Number/Letters/Number Pair

In this question, we are given a set of options: ABT, CEN, TOS, and AIO. We have to identify the odd word/number/letters/number pair from these alternatives.

To solve this question, let's analyze each option:

a) ABT: This is a combination of three letters, and there doesn't seem to be any specific pattern or reason behind it.

b) CEN: Similarly, this option is also a combination of three letters, and there doesn't seem to be any pattern or reason behind it.

c) TOS: Again, this option consists of three letters, but there is no apparent pattern or reason.

d) AIO: This option is different from the others because it consists of three letters, unlike the previous options. However, we can observe a pattern in this option. If we look closely, we can see that the letters A, I, and O are the first, ninth, and fifteenth letters of the alphabet, respectively. Therefore, the pattern seems to be based on the position of the letters in the alphabet.

Based on the analysis above, we can conclude that option D (AIO) is the odd one out because it follows a different pattern compared to the other options. The other options (ABT, CEN, and TOS) do not appear to follow any particular pattern or reason.

Therefore, the correct answer is option D (AIO).