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

Introduction / Context:
This spelling question requires you to select the correctly spelt word from several similar looking options. The word family is related to "actuate", which means to put into action or to motivate, and its noun form "actuation". Spelling questions like this test attention to detail and familiarity with common suffixes and word formation patterns in English.

Given Data / Assumptions:

• The options resemble variations of the same base word: "Actuasion", "Actation", "Actasion", "Actuation", and "Actuasionn".
• The intended correct English word is the noun derived from "actuate".
• We assume knowledge of similar words ending in "-tion".
• The question states that only one option is correctly spelt.
• We must identify the correct combination of root and suffix.

Concept / Approach:
The verb "actuate" gives rise to the noun "actuation" meaning the process of putting something into action. The standard pattern is verb plus "-ation": actuate to actuation. Many English nouns that describe processes or results of actions use the "-ation" ending, such as "motivate" to "motivation", "educate" to "education". Therefore, we should look for the form that follows this pattern accurately and is recognised in dictionaries.

Step-by-Step Solution:
Step 1: Recall the correct verb: "actuate". Step 2: Form the noun using the common pattern: remove the final "e" and add "-ation" to get "actuation". Step 3: Examine option "Actuasion". The ending "-asion" is incorrect for this word and does not match standard usage. Step 4: Examine "Actation". This appears to combine "act" with "-ation", but the established word is not "actation"; it is "action" or "actuation" depending on context. Step 5: Examine "Actasion". Again, the "-asion" ending is incorrect and not found in standard spelling for this word. Step 6: Examine "Actuation". This exactly matches the expected form "actuate" to "actuation". Step 7: Examine "Actuasionn". This adds an unnecessary extra "n" and also uses the wrong vowel combination. Step 8: Conclude that "Actuation" is the only correctly spelt word.

Verification / Alternative check:
We can verify by checking other words in the same pattern: "situation", "cultivation", "vibration". All feature the "-ation" ending. If we look at actual usage, phrases like "mechanical actuation" or "electronic actuation" are common in engineering and technology contexts. None of the other spellings appear in standard dictionaries or technical literature. This confirms that "Actuation" is the correct spelling.

Why Other Options Are Wrong:
"Actuasion" uses an improper vowel sequence "-uasion", which does not correspond to the known noun form. "Actation" is not the recognised noun derived from "actuate"; it could be mistaken for a combination of "act" and "nation" but has no established meaning. "Actasion" combines letters in a way that does not match any standard English word related to "actuate". "Actuasionn" introduces both an incorrect vowel sequence and an unnecessary extra consonant, making it doubly incorrect.

Common Pitfalls:
Test takers sometimes rely on approximate sound rather than visual familiarity, which leads them to pick forms like "-sion" or "-asion" incorrectly. English has many noun endings such as "-tion", "-sion", "-ation", and "-asion", but they are not interchangeable. Learning word families and noting how verbs convert into nouns can help avoid these errors. When unsure, think of related words and patterns rather than guessing from sound alone.

Final Answer:
The correctly spelt word is Actuation.