Explanation:

Let’s break it down step by step:

- The sequence is: TOC, SLX, RIS, QFN, ?

- Let’s look at each letter in the clusters and see if there’s a pattern in how they change.

First letters:

- T ? S ? R ? Q

- That’s alphabetical order, minus one each time (T, S, R, Q, then P as next). So the next starting letter should be P.

Second letters:

- O ? L ? I ? F

- O to L is -3, L to I is -3, I to F is -3

- So: F - 3 = C (using basic alphabetical order).

- The second letter should be C.

Third letters:

- C ? X ? S ? N

- C to X, alphabetically, C is 3rd, X is 24th in the alphabet, but let’s go backward:

- C (3rd), X (24th): 3, 24 ? Now, X to S (24 to 19, -5), S to N (19 to 14, -5)

- Let’s test: N - 5 = 14 - 5 = 9 ? 9th letter is I

So, putting together:

First: P

Second: C

Third: I

- Option 4 is PCI

Option: 4 PCI is correct.

Rest of the options:

- PDI: Second letter is wrong (should be C not D)

- PEI: Second letter is wrong (C not E)

- PCJ: Third letter is wrong (I not J)

That’s the logic. Pattern is: -1, -3, -5 across the three letters. Green check for you!