In the following question, four spellings of similar sounding words are given. Select the option that contains the correctly spelt English word.

Introduction / Context:
This spelling question tests your ability to recognise the standard spelling of English words, some of which are related to technical or formal contexts. Only one of the four options is correctly spelt, while the others contain common spelling mistakes. You must identify the correct form.

Given Data / Assumptions:

• Option A: rocketted.
• Option B: bienial.
• Option C: actuator.
• Option D: statuory.
• We assume standard modern British or American English spelling conventions.

Concept / Approach:
The word "actuator" is correctly spelt and is used in engineering and technology to mean a device that causes a machine to move or operate. The other three options are incorrect spellings of "rocketed", "biennial" and "statutory". Each of these real words is spelt differently in standard English, so they cannot be accepted as correct.

Step-by-Step Solution:
Step 1: Examine option C, "actuator". This is a valid English word, for example in the phrase "hydraulic actuator". Its spelling matches dictionary usage.Step 2: Check option A, "rocketted". The correct past tense form is "rocketed" with a single t in the middle, not double t t.Step 3: Check option B, "bienial". This looks like an incorrect attempt at "biennial", which refers to something occurring every two years and has a double n in the middle.Step 4: Check option D, "statuory". The correct spelling is "statutory", relating to a statute or law, with the sequence t u t o r y.Step 5: Because options A, B and D are all misspelt versions of common words, and option C matches the correct spelling of an actual English word, option C must be the answer.

Verification / Alternative check:
Consider dictionary forms and typical usage. You will find "actuator" used in technical manuals and engineering textbooks. Meanwhile, correct examples for the other words are "The price of fuel rocketed", "The commission submits a biennial report", and "The company must follow statutory regulations". The spellings in the question do not match these standard forms, confirming that only "actuator" is correct.

Why Other Options Are Wrong:
"Rocketted" adds an unnecessary extra t. "Bienial" drops one n that is essential in "biennial". "Statuory" misplaces letters and does not match the accepted form "statutory". All three would be marked wrong in any formal English exam or professional writing.

Common Pitfalls:
Students sometimes get confused by double consonants and similar patterns, especially in less familiar words. A good strategy is to develop the habit of visualising words as you see them in books, news articles and trusted websites. Repeated correct exposure helps fix the right pattern in memory and makes spelling questions easier over time.

Final Answer:
The correctly spelt word among the options is "actuator", so option C is correct.