In a certain code language, the word "BIOLOGY" is written as "YRLOLTB" using a mirror-alphabet substitution (Atbash-type) code. Using the same rule, how is the word "PHYSICS" written in that code language?

Introduction / Context:
This coding–decoding question uses a mirror-alphabet (Atbash) style cipher where each letter is replaced by its symmetric partner in the alphabet. The mapping is such that the positions of a letter and its code partner add up to 27 (A ↔ Z, B ↔ Y, C ↔ X, and so on). "BIOLOGY" is coded as "YRLOLTB" and we must extend this rule to "PHYSICS".

Given Data / Assumptions:

• "BIOLOGY" → "YRLOLTB".
• We must find the code for "PHYSICS".
• Alphabet positions: A = 1, B = 2, ..., Z = 26.
• For each pair (original letter, code letter), their positions sum to 27.

Concept / Approach:
First, verify that the letter pairs in BIOLOGY and YRLOLTB follow the Atbash rule. Once confirmed, we apply this mirror mapping to each letter of "PHYSICS". For any letter with position n, the coded letter has position 27 − n.

Step-by-Step Solution:
Step 1: Confirm the Atbash mapping with BIOLOGY. B (2) → Y (25); 2 + 25 = 27. I (9) → R (18); 9 + 18 = 27. O (15) → L (12); 15 + 12 = 27. L (12) → O (15); 12 + 15 = 27. O (15) → L (12); 15 + 12 = 27. G (7) → T (20); 7 + 20 = 27. Y (25) → B (2); 25 + 2 = 27. Every pair satisfies the Atbash condition. Step 2: Apply the same rule to PHYSICS. P (16): 27 − 16 = 11 → K. H (8): 27 − 8 = 19 → S. Y (25): 27 − 25 = 2 → B. S (19): 27 − 19 = 8 → H. I (9): 27 − 9 = 18 → R. C (3): 27 − 3 = 24 → X. S (19): 27 − 19 = 8 → H again. Step 3: Combine the coded letters. PHYSICS → K S B H R X H → "KSBHRXH".

Verification / Alternative check:
Atbash is symmetric: if you reapply the mapping to "KSBHRXH", you should get back "PHYSICS". Checking a couple of letters is enough to see that this is indeed the case, which confirms that the coding rule has been applied correctly.

Why Other Options Are Wrong:
Other options alter the position of letters or use letters that would correspond to non-Atbash shifts for some positions. For example, any option that does not end with H contradicts the fact that S must map to H under the mirror rule.

Common Pitfalls:
A frequent mistake is to use a fixed shift (like +2) and ignore the symmetrical nature of the mapping. Another pitfall is miscounting letter positions, especially in the middle of the alphabet.

Final Answer:
Using the same Atbash-style mirror coding, "PHYSICS" is written as KSBHRXH.