In this spelling recognition question, four words are provided and you must pick the one that is not spelt correctly.

Introduction / Context:
This question continues to test your ability to identify spelling errors in commonly used English words. Such questions are very common in competitive exams because they assess your attention to detail and your familiarity with standard written English. Here, you must decide which one of the four given words is incorrectly spelt.

Given Data / Assumptions:
- Options: 'Afforestation', 'Translusent', 'Foreigner', 'Achievement'.
- Exactly one word is incorrectly spelt, while the others are correct.
- All words are taken from general vocabulary related to environment, description, nationality and success.

Concept / Approach:
The key to this question is the adjective meaning 'allowing light to pass through but not detailed shapes'. The correct spelling is 'Translucent', not 'Translusent'. The 'lu' and 'u' positions are crucial. The other words—'Afforestation', 'Foreigner' and 'Achievement'—match their correct spellings as found in textbooks and dictionaries. You should mentally recall the root words and common suffixes to confirm each spelling.

Step-by-Step Solution:
Step 1: Check 'Afforestation'. This is correctly spelt and refers to planting trees on land that has not been forested for some time. Step 2: Check 'Translusent'. This looks suspicious because of the 'lus' sequence; the more familiar form is 'Translucent' with 'luc'. Step 3: Check 'Foreigner'. This is the correct spelling for a person from another country. Step 4: Check 'Achievement'. This is correctly spelt and refers to something accomplished successfully. Step 5: Confirm that the correct version of 'Translusent' is 'Translucent', with the 'luc' part reflecting the root related to light.

Verification / Alternative check:
You can relate 'Translucent' to the Latin root 'luc' meaning light, as also seen in 'lucid' (clear). Therefore 'Translucent' correctly has 'luc' in the middle, not 'lus'. Also, if you check a standard dictionary, 'Translusent' is not recognised as a valid spelling, while 'Translucent' is. The spellings of 'Afforestation', 'Foreigner' and 'Achievement' will also match the dictionary exactly, confirming that the only misspelt word is 'Translusent'.

Why Other Options Are Wrong:
'Afforestation' is correct and appears in environmental science texts with this exact spelling. 'Foreigner' is correct and should not be confused with incorrect forms like 'foriegner'. 'Achievement' is also correctly spelt following the pattern 'achieve' + 'ment'. Because none of these contain any letter order mistakes or extra letters, they cannot be chosen as the incorrectly spelt word.

Common Pitfalls:
Students often struggle with words derived from Latin roots and may not see the connection between related words like 'lucid', 'elucidate' and 'Translucent'. As a result, they may feel unsure and overthink. Another pitfall is focusing only on long words like 'Afforestation' or 'Achievement' and ignoring the shorter but trickier 'Translusent'. To avoid error, make a habit of noticing patterns in roots and suffixes while reading, which will help you quickly recognise when a familiar word looks slightly 'off'.

Final Answer:
The incorrectly spelt word is Translusent; it should correctly be written as 'Translucent'.