A pattern is formed with the letters O and X as follows: OXXXXX, XXXXO, OXXX, XXO, OX, ? Which of the following options correctly replaces the question mark to continue this pattern?

Introduction / Context:
This is a visual letter pattern question that uses only two characters, O and X. The series is OXXXXX, XXXXO, OXXX, XXO, OX, followed by a missing term. The key idea is that the number of X characters is decreasing by one at each step and the position of the single O alternates between the left and the right end in successive terms. Our goal is to extend this behaviour to determine the final term.

Given Data / Assumptions:

• Terms: OXXXXX, XXXXO, OXXX, XXO, OX, ? • Options: X, XO, OO, O • Assumption: The total length of each term reduces gradually as X characters are removed, with exactly one O in each term.

Concept / Approach:
We look at two separate patterns: the count of X characters, and the position of O within each string. The count of X decreases by one in each successive term, while the single O alternates between the leftmost and the rightmost position. Once these two patterns are clear, we can extrapolate to the next term, where the number of X becomes zero and only the behaviour of O matters.

Step-by-Step Solution:
Step 1: Count X characters in each term: • OXXXXX has five X. • XXXXO has four X. • OXXX has three X. • XXO has two X. • OX has one X. Step 2: The sequence of X counts is 5, 4, 3, 2, 1. The next count in this pattern must be 0. Step 3: Therefore, the last term should contain no X at all and must contain only O. Step 4: Observe O positions: in the first term O is on the left, in the second on the right, in the third on the left, in the fourth on the right, and in the fifth again on the left. Step 5: The O alternates between left and right. However, when there are zero X, there is only a single O left, so its position is simply O.

Verification / Alternative check:
We can summarise the pattern as: terms of length six, five, four, three, two, and finally one, with exactly one O and the remaining characters X. The count of X decreases by one each time while O moves from left to right alternately. With one X remaining in OX, the next term should remove that X, leaving just O. There is no way to create a length one string with X while preserving the decreasing count, so any answer containing X is inconsistent.

Why Other Options Are Wrong:
X contains one X and no O, which violates the rule that every term must include O and that the number of X should eventually drop to zero. XO has one X and one O, but that would continue the series with one X rather than reduce it to zero, breaking the clear descending X count. OO introduces two O characters, which has never occurred in the series and does not follow from the earlier pattern of exactly one O per term.

Common Pitfalls:
Some candidates focus only on the left right alternation of O and ignore the decreasing number of X, leading them to choose XO. Others may think only about length reduction and miss that there is always a single O and therefore the final term should contain only O when X count reaches zero. Tracking both count and position together prevents such errors.

Final Answer:
The pattern logically ends with a single O as the last term.