From the given alternative words, select the word which cannot be formed using the letters of the word COMMENTATOR.

Introduction / Context:
This word-formation question asks which word cannot be built from the letters of the base word COMMENTATOR. Each letter in COMMENTATOR can be used only as many times as it appears there. You must check letter availability and frequency for each option word and find the one that breaks the rules.

Given Data / Assumptions:
- Base word: COMMENTATOR.
- Letters: C, O, M, M, E, N, T, A, T, O, R.
- Frequencies: C(1), O(2), M(2), E(1), N(1), T(2), A(1), R(1).
- Options: MART, COMMON, MOMENT, CONTRACT.

Concept / Approach:
For each option, decompose the word into letters and compare how many times each letter is needed versus how many times it is available in COMMENTATOR. If an option requires any letter that does not exist in COMMENTATOR or requires more copies of a letter than available, that option cannot be formed. Exactly one of these will fail the test.

Step-by-Step Solution:
Step 1: Check MART: M, A, R, T. Required counts: M(1), A(1), R(1), T(1). COMMENTATOR has M(2), A(1), R(1), T(2). All are available in enough quantity, so MART can be formed. Step 2: Check COMMON: C, O, M, M, O, N. Required counts: C(1), O(2), M(2), N(1). COMMENTATOR provides exactly C(1), O(2), M(2), N(1). So COMMON can be formed. Step 3: Check MOMENT: M, O, M, E, N, T. Required counts: M(2), O(1), E(1), N(1), T(1). COMMENTATOR has at least these counts, so MOMENT can be formed. Step 4: Check CONTRACT: C, O, N, T, R, A, C, T. Required counts: C(2), O(1), N(1), T(2), R(1), A(1). COMMENTATOR has only C(1), which is not enough to supply two Cs. Therefore, CONTRACT cannot be formed.

Verification / Alternative check:
Reconfirm by listing available letters and “spending” them. After using letters for MART, COMMON or MOMENT, there are no conflicts with counts. For CONTRACT, however, immediately upon seeing two Cs in the spelling, you know there is a problem since COMMENTATOR contains only one C. This single mismatch is sufficient to disqualify CONTRACT.

Why Other Options Are Wrong:
- MART uses letters M, A, R, T, all supplied adequately by COMMENTATOR.
- COMMON uses two Ms, two Os, one C and one N, all of which match the base word's letter counts.
- MOMENT uses two Ms, one O, one E, one N and one T, again within available limits.

Common Pitfalls:
Students sometimes neglect to check repeated letters like C in CONTRACT or M and O in COMMON. They may also forget that each letter can only be used up to its count in the base word. A reliable strategy is to write down the exact letter frequencies for the base word first, then systematically compare each option against that list.

Final Answer:
The word that cannot be formed from COMMENTATOR is CONTRACT because it requires two Cs while COMMENTATOR has only one C.