In a certain language, the word "BROTHER" is written as "CSPUIFS". Using the same letter-shift code, how will the word "SISTER" be written in that language?

Introduction / Context:
This question belongs to the coding and decoding category where each letter of a word is transformed using a fixed rule. The candidate must observe the pattern in the given example and apply it consistently to a new word. This is a very common type in verbal reasoning sections of competitive exams.

Given Data / Assumptions:

• "BROTHER" is coded as "CSPUIFS".
• The transformation is letter by letter and deterministic.
• We need to find the coded form of "SISTER" using the same rule.
• All letters are in English uppercase alphabet, so standard alphabetical positions from A to Z apply.

Concept / Approach:
To decode the rule, we compare each letter in the original word "BROTHER" with its corresponding letter in the coded word "CSPUIFS". By checking alphabetical positions, we notice that every letter has been shifted forward by one place in the alphabet. For example, B goes to C, R goes to S and so on. Once the consistent pattern is recognized, we apply the same shift of plus one to each letter in the new word "SISTER".

Step-by-Step Solution:
Step 1: Write "BROTHER" and "CSPUIFS" in parallel and examine each pair of letters. Step 2: B becomes C, R becomes S, O becomes P, T becomes U, H becomes I, E becomes F and R becomes S. Step 3: In every case, the coded letter is one step ahead in the alphabet: B to C, R to S, O to P, T to U, H to I, E to F and R to S. Step 4: Conclude that the rule is "shift each letter one position forward in the alphabet." Step 5: Apply this rule to "SISTER". Step 6: S becomes T, I becomes J, S becomes T, T becomes U, E becomes F and R becomes S. Step 7: Therefore the coded form of "SISTER" is TJTUFS.

Verification / Alternative check:
We can check quickly by converting letters to numerical positions. S is 19, so S plus one is 20 which corresponds to T. I is 9, so I plus one is 10 which corresponds to J. Repeating this for all letters reproduces TJTUFS without inconsistency. Since the mapping is uniform and reversible, the code is consistent and reliable.

Why Other Options Are Wrong:
TJTFUS and TJTSFU differ from the correct form by swapping or misplacing letters, which would violate the uniform shift rule. SFUTJT mixes the letters in a more complex way and cannot be derived by adding one to each original letter. These options exist to trap candidates who guess or misread the order of letters instead of applying the precise pattern from the example.

Common Pitfalls:
The most common mistakes include shifting letters in the wrong direction, such as subtracting one instead of adding one, or accidentally altering the order of letters while coding. Another error is to assume a more complicated pattern than necessary. Carefully comparing each original letter with its coded counterpart usually reveals a simple shift rule that should then be applied consistently to the target word.

Final Answer:
Using the same plus one alphabetical shift that turns "BROTHER" into "CSPUIFS", the word "SISTER" is coded as TJTUFS.