In the following question, out of the four alternatives, choose the word that best expresses the meaning of the given word CONSTRAIN.

Introduction / Context:
Synonym questions test a learner's ability to match a given word with another word that has a very similar meaning in most contexts. The word CONSTRAIN appears in many formal texts, including legal documents, reports, and academic writing. It often describes limiting the freedom of actions, feelings, or development. Choosing the right synonym helps improve both comprehension and precise expression in English.

Given Data / Assumptions:

• Target word: CONSTRAIN.
• Options: STRESS, CONTRADICT, RESTRICT, OBSTRUCT.
• We must select the word that comes closest in meaning across common contexts.
• Standard dictionary meanings of these words are assumed.

Concept / Approach:
To constrain someone or something is to force them to act in a certain way or to limit their freedom or possibilities. In ordinary usage, it is close in meaning to restrict, limit, or confine. The word RESTRICT captures exactly this sense of limiting freedom or scope. STRESS refers to mental or physical pressure, CONTRADICT means to deny or oppose a statement, and OBSTRUCT means to block the way, usually physically. Only RESTRICT consistently overlaps with the core meaning of CONSTRAIN in abstract and practical contexts.

Step-by-Step Solution:
Step 1: Recall that CONSTRAIN means to limit, restrict, or compel, often by applying rules, circumstances, or pressure. Step 2: Examine STRESS, which means mental strain or emphasis, not primarily about limiting freedom of action. Step 3: Examine CONTRADICT, which means to state the opposite of what someone else has said, focusing on disagreement in statements, not limitation. Step 4: Examine RESTRICT, which means to limit the size, amount, or range of something, or to control someone's activities by rules. Step 5: Examine OBSTRUCT, which means to block or get in the way of something, usually in a physical sense like obstructing a road. Step 6: Notice that RESTRICT best matches the idea of limiting or confining action, very close to CONSTRAIN. Step 7: Conclude that RESTRICT is the best synonym among the given options.

Verification / Alternative check:
Consider example sentences. Circumstances constrained him to accept the job can be rewritten as Circumstances restricted him to accepting the job without much change in meaning. However, replacing constrained with stressed, contradicted, or obstructed does not work. For instance, Circumstances stressed him to accept the job sounds odd and inaccurate. Similarly, The law constrains pollution levels can be restated as The law restricts pollution levels. This parallel confirms that RESTRICT is the closest match in sense and usage.

Why Other Options Are Wrong:
STRESS is wrong because it describes pressure or emphasis but does not directly mean to limit or confine, although stress can sometimes lead to constrained behaviour. CONTRADICT is wrong because it deals with opposing statements rather than boundary setting. OBSTRUCT focuses on blocking progress, especially physically, and is more specific than the broader, often abstract sense of CONSTRAIN. None of these words can be substituted for CONSTRAIN in many standard sentences without altering the meaning significantly.

Common Pitfalls:
A typical mistake is to choose OBSTRUCT because students think of any kind of difficulty as a constraint. However, obstruction is about blockage, whereas constraint is broader and often involves rules, limits, or internal factors. Another pitfall is to pick STRESS because pressure can cause constrained actions, but the words are not interchangeable. A good strategy is to remember that CONSTRAIN and RESTRICT both fit naturally into phrases like constrain growth or restrict growth, which is a strong clue for the correct answer.

Final Answer:
The word that best expresses the meaning of CONSTRAIN is RESTRICT.