From the given words, select the word that cannot be formed using the letters of the word DISSERTATION.

Introduction / Context:
This word formation question uses the base word DISSERTATION. You must choose which of the given options cannot be formed from its letters. All options resemble the base word to some degree, but one of them contains a letter that is not present in DISSERTATION. The aim is to test your attention to detail and your ability to match letters and their frequencies accurately, an important aspect of verbal reasoning for competitive examinations.

Given Data / Assumptions:
Base word: DISSERTATION.
Letters available: D, I, S, S, E, R, T, A, T, I, O, N.
Options: SISTER, STATION, DIRECTION, RATION.
We assume each letter from the base word may be used at most as many times as it appears, and no new letters may be added.

Concept / Approach:
The method is to list the letters available and then check each option one by one. A word is impossible if it contains a letter missing from the base word or if it requires more copies of a letter than are available. Because the base word is long and options are drawn from common English vocabulary, it is easy to be misled by superficial similarity, so a careful letter based check is essential.

Step-by-Step Solution:
Step 1: Count letters in DISSERTATION. D: 1, I: 2, S: 2, E: 1, R: 1, T: 2, A: 1, O: 1, N: 1. Step 2: Check SISTER. SISTER requires S, I, S, T, E, R. The base word has S twice, I twice, T twice, E once and R once, so SISTER can be formed. Step 3: Check STATION. STATION requires S, T, A, T, I, O, N. All these letters exist in DISSERTATION with adequate counts, so STATION is possible. Step 4: Check RATION. RATION requires R, A, T, I, O, N. DISSERTATION has each of these letters at least once, so RATION can also be formed. Step 5: Check DIRECTION. DIRECTION requires D, I, R, E, C, T, I, O, N. The letter C is needed, but there is no C in DISSERTATION. Therefore DIRECTION cannot be formed from DISSERTATION.

Verification / Alternative check:
Reexamine the base word letters: D, I, S, S, E, R, T, A, T, I, O, N. There is clearly no C. Since DIRECTION requires C, it is impossible to construct. For SISTER, STATION and RATION, every letter appears in the base word within the available counts. Thus there is exactly one invalid option, confirming that DIRECTION is the correct answer for this question.

Why Other Options Are Wrong:
SISTER is valid because it uses S, I, T, E and R, all present in the base word, and does not exceed their frequencies.
STATION is valid since S, T, A, T, I, O and N all occur in DISSERTATION and are available in sufficient numbers.
RATION is valid as R, A, T, I, O and N can be taken directly from the base word without any shortage.
These three options therefore can be formed and are not the word that the question asks you to identify.

Common Pitfalls:
Because the base word is long and complex, candidates sometimes assume that any familiar looking word, like DIRECTION, can be formed from it. In reality, a single new letter is enough to invalidate an option. Another pitfall is focusing only on vowel presence and ignoring critical consonants such as C. A robust strategy is to scan each option for any letter not listed in the base word before checking frequencies. This immediately reveals DIRECTION as impossible due to the missing C.

Final Answer:
The word that cannot be formed from the letters of DISSERTATION is DIRECTION, because the base word does not contain the letter C.