Identify the block that completes the repeating mirror-pattern: H — JH — IJHHI — HH — JH. Choose the option that best fits the missing block (letters only, no separators).

Introduction / Context:
Letter-and-symbol series may be built by concatenating short “blocks” that themselves have internal symmetry. Recognizing those building blocks is the key.

Given Data / Assumptions:

• Visible sequence (blocks separated by dashes here for clarity): H — JH — IJHHI — HH — JH.
• We assume the missing piece is a compact block that preserves the symmetric/mirror flavor already visible in “IJHHI”.

Concept / Approach:
Decompose what we see: “IJHHI” is a 5-letter palindrome (I–J–H–H–I). Flanking it, we have left-side growth “H, JH” and right-side echo “HH, JH”. The missing block between “H” and “JH” should reconcile transitions from singleton H to the long central palindrome and then back toward “JH”. A natural candidate is a near-mirror of the edges around “IJHHI” that starts with I and ends with J, maintaining adjacency harmony: “IHIJ”.

Step-by-Step Solution:

Verification / Alternative check:
Try inserting other options: “IHJI”, “HIHI”, or “HJHJ”. Each either breaks the palindromic alignment or causes awkward bigrams at the joins (e.g., duplicated J at the “JH” junctions) that disrupt the intended symmetry flow.

Why Other Options Are Wrong:
“IHJI” and “HJHJ” are not consistent mirrors of the core and create uneven transitions; “HIHI” repeats a 2-letter loop that does not integrate with the central 5-letter palindrome’s boundaries.

Common Pitfalls:
Assuming the missing piece must also be a strict palindrome; sometimes a near-mirror bridge fits better between asymmetric neighbors.

Final Answer:
IHIJ.