In the following letter series analogy, BPTW is related to CQUX. Using the same pattern, CHNS is related to which of the following letter groups?

Introduction / Context:
This is a letter series analogy based on shifting each letter forward by a fixed number of positions. The pair BPTW and CQUX shows a systematic change which must be applied to the next term CHNS. Letter shifting patterns of this kind are frequently tested in reasoning examinations to check comfort with alphabetical sequences.

Given Data / Assumptions:

• First pair: BPTW : CQUX
• Second first term: CHNS
• Options: DIST, DIOT, BGOT, DSTO.
• Letters follow the A to Z ordering with positions 1 to 26.

Concept / Approach:
When the same number is added to the positions of each letter in a group to obtain another group, we have a simple shift cipher. To reuse this transformation, we must first determine how BPTW changes into CQUX. After discovering the shift, we will apply it to CHNS and see which option matches exactly.

Step-by-Step Solution:
Step 1: Convert BPTW into positions. B is 2, P is 16, T is 20, and W is 23. Step 2: Convert CQUX into positions. C is 3, Q is 17, U is 21, and X is 24. Step 3: Compute the change for each position. B to C is plus 1, P to Q is plus 1, T to U is plus 1, and W to X is plus 1. Step 4: Conclude that the transformation adds 1 to the alphabet position of every letter. Step 5: Apply this rule to CHNS. Positions: C is 3, H is 8, N is 14, S is 19. Step 6: Add 1 to each position. C plus 1 is D (4), H plus 1 is I (9), N plus 1 is O (15), and S plus 1 is T (20). Step 7: Combine these letters to get DIOT.

Verification / Alternative check:
We can verify by checking DIOT against the choices. DIOT appears as an option and matches the plus one shift pattern exactly. For thoroughness, small checks show that DIST, BGOT, and DSTO require different letter by letter changes and are not uniform plus one transformations of CHNS. Hence only DIOT correctly follows the established rule.

Why Other Options Are Wrong:
DIST would involve changing C to D, H to I, N to S, and S to T, which is not a consistent plus one mapping because N to S is a plus five shift. BGOT and DSTO likewise have mixed shifts that do not mirror the uniform transformation from BPTW to CQUX. Since the first pair clearly changes every letter by exactly one position, any option that does not maintain this consistency must be rejected.

Common Pitfalls:
Some candidates may match only the first two letters of a candidate option and ignore the rest. This can lead to mistakenly selecting an option that partially fits. To solve such questions reliably, always compute and verify the transformation for every letter in the group. Writing out positions is a simple technique that can prevent errors caused by visual similarity alone.

Final Answer:
The group of letters that correctly completes the analogy BPTW : CQUX :: CHNS : ? is DIOT.