Four different spellings of the same word are given below. Only one of them is spelt correctly in standard English. Carefully read each option and choose the correctly spelt word.

Introduction / Context:
Spelling based questions test your familiarity with standard English orthography. Many English words, especially those of older origin, have silent letters or unusual letter combinations. The word in focus here is thoroughly, which is commonly used to mean completely, in detail, or very carefully. You are given four alternative spellings and must identify the one that matches the correct dictionary form of the word.

Given Data / Assumptions:
- The target word means completely or very carefully. - Four candidate spellings are presented: Thoruoghly, Thoroughly, Thoroghouly, and Thorougholy. - Only one of these is standard and correct.

Concept / Approach:
English spelling often follows patterns, particularly in common suffixes. The adverb thoroughly is formed from the adjective thorough plus the adverbial suffix ly. The base word thorough is spelt t h o r o u g h and the full adverb is t h o r o u g h l y. To decide which option is correct, break it into the recognised base and suffix and check for extra or misplaced letters. Options that disturb the pattern of thorough plus ly are incorrect.

Step-by-Step Solution:
Step 1: Recall or infer that the base word is thorough, which ends with the sequence ough. Step 2: Form the adverb by adding ly directly after thorough, giving thoroughly. Step 3: Examine option A, Thoruoghly, where the letters u and o are incorrectly arranged inside the word. Step 4: Examine option B, Thoroughly, which preserves the base thorough and adds ly correctly. Step 5: Examine option C, Thoroghouly, which inserts an extra o and rearranges the ough cluster incorrectly. Step 6: Examine option D, Thorougholy, which breaks the base and suffix pattern by inserting an extra o before the final ly.

Verification / Alternative check:
You can verify the spelling by thinking of related forms like thoroughness or by recalling common usage in reading. Standard dictionaries consistently record the adverb as thoroughly. Another strategy is to mentally pronounce each option and check if any strange additional syllables appear due to extra letters. The options with scrambled ough clusters produce awkward imaginary pronunciations, confirming that they are incorrect. Only option B maintains the standard letter sequence and recognisable pronunciation.

Why Other Options Are Wrong:
Option A is wrong because the letters u and o are misplaced, breaking the thorough pattern. Option C is wrong because it overcomplicates the middle of the word with an incorrect ordering of vowels. Option D is wrong because of an unnecessary extra o before ly, which does not appear in the correct word.

Common Pitfalls:
Learners often struggle with words that contain ough, as this group of letters appears in many different pronunciations and positions. Confusion increases when similar looking wrong options are presented. To avoid such mistakes, make a habit of noting down and revising commonly tested words like thorough, although, through, and thought. Visual memory of the correct form is very helpful. Anchoring the pattern thorough plus ly in your mind will help you quickly eliminate incorrect variants in exams.

Final Answer:
The correctly spelt word is Thoroughly.