Question

His manners have undergone a huge change since his association with his new partners. 

• A. a sea change
• B. a big change
• C. a vast change
• D. an oceanic change
• E.

Hint:

A sea change refers to a profound or significant change, especially in character or behavior.

Answer 1

The Correct Option is A

The phrase a sea change refers to a significant and profound transformation. It fits perfectly in the context of a dramatic change in someone's manners. - Option (B) a big change is too general and doesn't convey the depth of transformation implied in the sentence. - Option (C) a vast change doesn't have the same idiomatic meaning as a sea change. - Option (D) an oceanic change is not a common idiom. Therefore, a sea change (Option A) is the most appropriate choice. 

Answer 2

The sentence needs an expression for a dramatic, thorough transformation, so testing each option for whether it is an established idiom of that specific intensity, rather than just a generic description of change, resolves the choice.

1. Option A: "a sea change" is a well-established idiom specifically describing a profound and complete transformation, precisely matching the dramatic shift in manners described in the sentence.
2. Option B: "a big change" is a plain, generic description of change that lacks the specific idiomatic weight of describing a truly profound transformation.
3. Option C: "a vast change" similarly describes size or extent in a general way without carrying the recognised idiomatic sense that "sea change" specifically conveys.
4. Option D: "an oceanic change" attempts a similar water-related image but is not an established English idiom, unlike "sea change."

Only option A is the recognised idiom for a dramatic transformation, matching the sentence's context.

Hence, the correct answer is Option A.