In English vocabulary, select the antonym that best expresses the opposite meaning of the word "virtuous", which describes a person who is morally good and behaves with high ethical standards.

Introduction / Context:
The adjective "virtuous" is frequently used in moral, religious, and ethical discussions to describe people who act with integrity, honesty, and high moral principles. To solve this question correctly, a learner must clearly understand not only what virtuous means but also how English forms exact opposites for moral qualities. Examinations often test antonyms of such value loaded words because they appear in essays, moral stories, and editorials that discuss character and behaviour.

Given Data / Assumptions:
- The tested word is the adjective "virtuous". - "Virtuous" refers to moral excellence and good character. - The question asks specifically for the antonym, that is, the opposite meaning. - Only one option gives a clear opposite; others are either similar or unrelated.

Concept / Approach:
Virtuous is used to describe someone who consistently does what is morally right. Therefore the antonym should describe a person or behaviour that is morally bad, wicked, or corrupt. When dealing with questions on antonyms, it is helpful to group words into semantic fields. Virtuous belongs to a positive moral field, while words like wicked, evil, or vile belong to the negative side. Meanwhile, some of the options in this question actually describe goodness or purity, which are similar in meaning to virtuous and are therefore not correct antonyms.

Step-by-Step Solution:
Step 1: Recall that "virtuous" is used for people who follow moral rules, show honesty, kindness, and self control. Step 2: Look at option a, "vile". Vile means extremely unpleasant, morally bad, or disgusting in character. This clearly stands on the opposite end of the moral spectrum. Step 3: Examine option b, "chaste". Chaste describes purity, especially with respect to sexual behaviour, and often carries a positive moral sense, which is close to virtuous, not opposite. Step 4: Examine option c, "kosher". In informal English, kosher can mean proper or legitimate, and in a religious sense it refers to food that meets certain purity laws. It again suggests correctness and acceptability, not moral corruption. Step 5: Examine option d, "celibate". Celibate describes a person who does not marry or does not engage in sexual relations, often for religious or personal reasons, and it is not a direct value judgement of total moral character. Step 6: Since only "vile" captures the idea of moral badness that clearly contrasts with "virtuous", it is the correct antonym.

Verification / Alternative check:
One simple verification is to create a sentence pair. Consider the phrase "a virtuous leader" which implies honesty and integrity. A natural opposite expression would be "a vile leader", indicating corruption and cruelty. The alternative pairs "a virtuous leader" and "a chaste leader" or "a virtuous leader" and "a kosher leader" do not create an opposite contrast; instead they both sound positive. This demonstrates that vile is the only option that reverses the positive moral judgement implied by virtuous.

Why Other Options Are Wrong:
Option b "chaste" is wrong because it describes moral or sexual purity, which aligns more with virtuous rather than opposing it. Option c "kosher" is wrong since it indicates something proper, acceptable, or lawful, again closer to virtue than to vice. Option d "celibate" is wrong because it mainly refers to marital or sexual abstinence and does not convey general moral badness.

Common Pitfalls:
Candidates sometimes confuse words from similar moral domains, assuming that any word used in religious or ethical contexts must be an antonym. In reality, many such words are near synonyms. Another mistake is to be misled by unfamiliar terms like "kosher" and to select them simply because they sound foreign or technical. For vocabulary questions, the safest strategy is always to focus on the core meaning and to ask whether a word truly reverses the original sense or merely shifts the focus to a narrow aspect of behaviour.

Final Answer:
The correct antonym of "virtuous" in this question is vile.