In the following question, four words are given, out of which only one is correctly spelt. Select the correctly spelt word.

Introduction / Context:
This spelling question checks whether you can recognise the standard spelling of a technical noun often used in engineering and manufacturing. You are given four similar looking words and must select the one that is correctly spelt in standard English. Accurate spelling is important in both exams and professional communication.

Given Data / Assumptions:

- Options: Extrution, Extrusion, Extrosion, Extrotion. - Only one of these represents the correct spelling of a real English word. - The target word relates to a process of shaping material by forcing it through a die. - The other options are misspellings intended to test attention to detail.

Concept / Approach:
Extrusion is the correct spelling of the word that describes a process in which material is pushed through a shaped opening to produce objects like pipes or rods. The central sequence in the word is trus, not trut, tros, or trot. The other choices contain incorrect vowel or consonant combinations and do not appear in dictionaries as standard words in this sense.

Step-by-Step Solution:
Step 1: Recall where you may have seen the word, for example in phrases like plastic extrusion or aluminium extrusion. Step 2: Remember that the correct spelling uses the root extrude and adds the suffix sion, giving extrusion. Step 3: Examine option B, Extrusion. This matches the expected pattern and looks familiar from technical usage. Step 4: Look at option A, Extrution, which replaces the sion ending with tion and drops the s, making it an incorrect variant. Step 5: Check option C, Extrosion, which changes the middle consonant cluster and does not correspond to any recognised English word. Step 6: Consider option D, Extrotion, which resembles extortion but is not the word we are targeting and is therefore wrong. Option B remains the only correct choice.

Verification / Alternative check:
Use online reading or textbooks as a mental reference. In engineering contexts, you will see headings like Extrusion process or Types of extrusion. Spelling it as Extrution, Extrosion, or Extrotion would be marked as a spelling mistake. You can also break the word into ext plus rusion, remembering that words ending in sion often connect to verbs ending in de, such as intrude and intrusion, extrude and extrusion.

Why Other Options Are Wrong:
Extrution drops the s that is needed in the sion ending and does not follow the usual spelling pattern. Extrosion inserts an r in the wrong place and does not correspond to any accepted English term. Extrotion looks like a mistaken blend of extrusion and extortion; it is not a dictionary word and does not carry the intended meaning related to shaping materials.

Common Pitfalls:
When words are unfamiliar, students sometimes rely on guesswork based on sound alone. However, English spelling often follows patterns, especially with common suffixes like sion and tion. Learning root and suffix pairs, such as extrude and extrusion, helps you recognise correct spellings even for technical terms. Reading subject specific material also reinforces the correct forms visually.

Final Answer:
Extrusion is the correctly spelt word.