Find the missing term in the series.
ACE, EGI, IKM, MOQ, ?

The correct option is QSU.

To find the missing term in the letter series ACE, EGI, IKM, MOQ, ?, let us analyze the pattern by looking at the position of each letter in the English alphabet.

First, let us examine the first letter of each group:

$\text{A}\stackrel{+4}{\to }\text{E}\stackrel{+4}{\to }\text{I}\stackrel{+4}{\to }\text{M}\stackrel{+4}{\to }\text{Q}$

Alphabetical positions for the first letters: A (1), E (5), I (9), M (13). Adding 4 to 13 gives 17, which corresponds to the letter Q.

Next, let us examine the second letter of each group:

$\text{C}\stackrel{+4}{\to }\text{G}\stackrel{+4}{\to }\text{K}\stackrel{+4}{\to }\text{O}\stackrel{+4}{\to }\text{S}$

Alphabetical positions for the second letters: C (3), G (7), K (11), O (15). Adding 4 to 15 gives 19, which corresponds to the letter S.

Finally, let us examine the third letter of each group:

$\text{E}\stackrel{+4}{\to }\text{I}\stackrel{+4}{\to }\text{M}\stackrel{+4}{\to }\text{Q}\stackrel{+4}{\to }\text{U}$

Alphabetical positions for the third letters: E (5), I (9), M (13), Q (17). Adding 4 to 17 gives 21, which corresponds to the letter U.

Combining the resulting letters gives QSU.