In this English usage question on sentence improvement, consider the sentence She was unhappy even after she married into an accommodative and caring family, in which the underlined verb phrase describes her continuing emotional state. Select the option that best expresses the idea that her unhappiness continued even after her marriage, without changing the basic meaning, and choose No improvement only if the original wording is fully satisfactory.

Introduction / Context:
This question examines subtle choices in vocabulary and aspect when describing an ongoing state. The sentence refers to a woman who did not become happy even after she married into a caring family. The underlined part uses was unhappy, which is grammatically correct but may not capture the idea of continuation as strongly as another option. You must select the expression that best shows that her unhappiness persisted after the marriage and that fits naturally in formal English.

Given Data / Assumptions:

• The sentence context is emotional state before and after marriage.
• The underlined expression is was unhappy.
• The options are remained unhappy, continued her sadness, existed in unhappiness, and No improvement.
• The goal is to choose the most natural and precise description of the continuing state.

Concept / Approach:
Verbs like remain and continue are often used to express a state that persists over time. Although was unhappy is correct, the exam is checking whether any alternative gives a more precise and idiomatic expression for the idea that her unhappiness did not change even after marriage. The phrase remained unhappy is a common collocation in English and clearly highlights that her emotional state stayed the same. Other options sound awkward or are not usual combinations in natural usage. Therefore, the approach is to pick the alternative that best fits standard collocations and emphasises continuity.

Step-by-Step Solution:
First, understand that the key idea is that she was unhappy before marriage and that this unhappiness did not disappear after she joined an accommodative and caring family. Second, recognise that the exam often prefers verbs that explicitly signal continuation of a state, and remained is a typical choice here. Third, compare the options and check them against standard English collocations, for example remained unhappy is common and clear. Fourth, see that continued her sadness does not sound natural because sadness is not usually something we continue in this way, and existed in unhappiness sounds clumsy and overly abstract. Fifth, choose remained unhappy as the best alternative that preserves the intended meaning and improves the style.

Verification / Alternative check:
To check, create similar sentences such as He remained unhappy despite getting a promotion or She remained unhappy even after the problem was solved. These examples sound normal and are listed in many language resources. On the other hand, He continued his sadness or She existed in unhappiness are not forms that native speakers commonly use. Although was unhappy is not wrong, exam style often rewards a more precise verb when it is offered among the choices, and remained unhappy clearly does this job.

Why Other Options Are Wrong:
Option B, continued her sadness, treats sadness as an object of continue in an unnatural way; English usually says continued to be sad or remained sad, not continued her sadness.

Option C, existed in unhappiness, is grammatically possible but sounds very heavy and abstract for ordinary narrative style, and it is not a common collocation.

Option D, No improvement, ignores the fact that remained unhappy gives a more precise sense of ongoing state, which is likely what the exam setter wants to highlight.

Common Pitfalls:
Learners sometimes think that any grammatically correct expression is automatically the best choice, but sentence improvement questions are about selecting the most natural and idiomatic form. Another pitfall is focusing only on vocabulary meaning without checking how words combine in real usage. Paying attention to common phrases such as remain unhappy, remain calm, remain silent, and so on can help in choosing more native like expressions in exams.

Final Answer:
The option that most naturally and clearly shows that her unhappy state continued after marriage is remained unhappy.