Explanation:

Let’s break down the problem:

- Here’s the sequence: QKYF, NIUA, ?, HEMQ, ECIL.

- To spot the pattern, compare the first letters: Q?N???H?E. Each letter is moving back by 3 in the alphabet:

- Q (17), N (14), ? (11), H (8), E (5)

- So, after N comes K.

- Next letters: K?I???E?C.

- K (11), I (9), ? (7), E (5), C (3)

- So, after I comes G.

- Third letters: Y?U???M?I.

- Y (25), U (21), ? (17), M (13), I (9)

- Subtracting 4 each time, after U comes Q.

- Fourth letters: F?A???Q?L.

- F (6), A (1), ? (22), Q (17), L (12)

- Here it looks odd. There’s a backward jump: F (6), A (1), Q (17), Q (17), L (12).

- Actually, after A (1), if you subtract 5, you get a negative number, so maybe it’s cycling back from Z (26).

- If we do this: A (1) - 5 = -4. Add 26: 22, which is V (but that doesn't match).

- Sequence: F (6), A (1), Q (17), Q (17), L (12)

- Now, look at the options for third letter: Only "Q" (KGQV, KHQV, KGQV) is at position 17. So Q likely fits.

- Comparing the third option (KGQV):

- K, G, Q, and V

- K is 11, should be, check above: Yes.

- G is 7, ok.

- Q is 17, ok.

- V is 22.

- Fourth letters: F (6), A (1), V (22), Q (17), L (12).

- Pattern is: -5, +21, -5, -5

What this really means is, option 3 fits the pattern best.

- Option 1: KGRV—the third letter is R instead of Q.

- Option 2: KHQV—second letter is H instead of G.

- Option 4: KGRW—last letter is W not fitting the jump.

- Option 3: KGQV—this one checks out through sequencing.

So, the answer is:

Option 3: KGQV