From the given options, select the word that cannot be formed using the letters of the word ENDEAVOUR.

Introduction / Context:
This is a word formation question based on the base word ENDEAVOUR. You must decide which of the given options cannot be formed by rearranging some or all of the letters in ENDEAVOUR, without adding any extra letters and without reusing letters beyond their available count. Questions like this test your ability to track letters accurately, pay attention to missing characters, and apply systematic checking under time pressure, which is an important skill in verbal reasoning sections of competitive exams.

Given Data / Assumptions:
Base word: ENDEAVOUR.
Letters available: E, N, D, E, A, V, O, U, R.
Options: Devour, Round, Drown, Drove.
We assume that letters are case insensitive and that each letter in the base word can be used at most as many times as it appears in ENDEAVOUR.

Concept / Approach:
The correct strategy is to first list the letters and their frequencies from ENDEAVOUR and then check each option letter by letter. Any option that uses a letter not present in the base word, or uses a letter more times than allowed, cannot be formed from the base word. Since the words are fairly short, this analysis can be done quickly. It is efficient to first scan for obviously absent letters, as that immediately eliminates an option without further counting.

Step-by-Step Solution:
Step 1: Count the letters in ENDEAVOUR. E appears 2 times, N 1 time, D 1 time, A 1 time, V 1 time, O 1 time, U 1 time, R 1 time. Step 2: Check Devour. Devour requires D, E, V, O, U, R. All these letters exist in ENDEAVOUR with sufficient counts, so Devour can be formed. Step 3: Check Round. Round requires R, O, U, N, D. All five letters appear at least once in ENDEAVOUR, so Round can be formed. Step 4: Check Drove. Drove requires D, R, O, V, E. Each of these letters is available, and none is overused, therefore Drove can also be formed. Step 5: Check Drown. Drown requires D, R, O, W, N. The letter W does not appear in ENDEAVOUR at all, so it is impossible to form Drown from ENDEAVOUR. Hence Drown is the word that cannot be formed.

Verification / Alternative check:
As a verification step, scan the base word again: E, N, D, E, A, V, O, U, R. Clearly, W is absent. The other letters needed for Drown, namely D, R, O, and N, are present, but without W, the word cannot be completed. For Devour, Round and Drove, every letter appears in the base word and fits within the available counts. Therefore, there is exactly one invalid option, confirming that our choice is correct.

Why Other Options Are Wrong:
Devour is valid because all its letters D, E, V, O, U, R are present in the base word.
Round is valid since R, O, U, N, and D all occur in ENDEAVOUR, and no letter is used more than available.
Drove is also valid because D, R, O, V, and E can all be taken from ENDEAVOUR without exceeding letter frequencies.
These words therefore can be formed and do not answer the question, which specifically asks for the word that cannot be formed.

Common Pitfalls:
Students may hurry and miss a single letter like W, especially when the rest of the letters fit nicely. Another pitfall is to assume that if a word looks similar to the base word, it must be possible to form it, without doing a thorough letter check. To avoid such mistakes, always scan for any letter in the option that does not appear at all in the base word, as that immediately eliminates that option. Also remember to consider repeated letters and verify that their counts do not exceed those in the base word.

Final Answer:
The only option that requires a letter not present in ENDEAVOUR is Drown, because it needs W, which the base word does not contain. Hence Drown is the correct answer.