In the letter series A, C, E, G, ?, which letter should replace the question mark to continue the pattern?

Introduction / Context:
This is a straightforward single letter series: A, C, E, G, ?, where you must identify the next letter. Questions like this test recognition of simple arithmetic progressions in alphabet positions. Because only one letter is missing and the steps are small, this is considered an easy level question.

Given Data / Assumptions:

• Given letters: A, C, E, G, ?
• Alphabet positions: A 1, B 2, C 3, D 4, and so on up to Z 26.
• The series appears to be strictly increasing and uses only consonants and vowels in a regular fashion.

Concept / Approach:
The best approach is to convert each letter into its numeric position, compute the differences between consecutive terms, and see whether a constant difference emerges. If so, we simply add the same difference to the last term to get the position of the missing letter. Finally, we map that position back to its corresponding letter.

Step-by-Step Solution:
Step 1: Replace each letter with its position: A 1, C 3, E 5, G 7. Step 2: Compute the differences between consecutive terms: 3 minus 1 equals 2, 5 minus 3 equals 2, and 7 minus 5 equals 2. Step 3: The difference is a constant +2 throughout the series. Step 4: Continue this pattern by adding 2 to the last position. 7 plus 2 equals 9. Step 5: The 9th letter of the alphabet is I. Step 6: Therefore, the missing letter that continues the series is I.

Verification / Alternative check:
We can rewrite the full series including the answer as A (1), C (3), E (5), G (7), I (9). This is simply all odd numbered positions from 1 to 9, stepping by 2. No other option gives such a neat arithmetic progression. If we tried H (8) or J (10), the difference pattern of plus 2 would break at the missing term.

Why Other Options Are Wrong:
H corresponds to position 8, which would create a jump of +1 from G 7 to H 8 instead of +2. J is 10, which would give a jump of +3 from 7, again breaking the constant difference pattern. F is 6, which would move backwards and disrupt the simple increasing sequence. K is 11, and going from 7 directly to 11 would be a jump of +4, which does not match the established difference.

Common Pitfalls:
Some candidates guess based on visual familiarity with letters (for example, thinking of common letter pairs like G and H) without actually calculating positions. Others may incorrectly assume a mixture of increments, but with four terms already provided, it is easy to see that the consistent difference is +2. Converting to numeric positions and checking the differences is the safest method.

Final Answer:
The letter that completes the series is I.