In this one-word substitution question, choose the single English word that best expresses the phrase "insatiable greed for riches", that is, an excessive and never-ending desire for wealth.

Introduction / Context:
This question examines your knowledge of one-word substitutions, an important area of English vocabulary in competitive exams. Instead of using a long phrase like "insatiable greed for riches", English has a precise word that condenses the entire meaning. Recognising such words improves both comprehension and expression, especially in formal writing and objective tests.

Given Data / Assumptions:
We are given the descriptive phrase "insatiable greed for riches". We must select the single word that accurately represents this idea. We assume standard dictionary meanings of all options.

Concept / Approach:
The key words in the phrase are "insatiable" (never satisfied), "greed" (excessive desire), and "riches" (wealth, money, material possessions). In English, the classical term that combines greed and wealth is "avarice". It comes from Latin and is frequently used in literature, moral essays, and even religious or philosophical texts to criticise excessive love of money.

Step-by-Step Solution:
Step 1: Focus on the idea of greed for money or wealth, not just ordinary desire. Step 2: Recall that "avarice" is defined as extreme or insatiable greed for wealth. Step 3: Compare "avarice" with the other options and see that none of them refers to greed. Step 4: Confirm that "avarice" matches the phrase almost word for word. Step 5: Select Option A as the correct substitution.

Verification / Alternative check:
To verify, consider well-known phrases such as "the sin of avarice" or "blinded by avarice", which clearly indicate destructive greed for money. Dictionaries typically gloss "avarice" as "extreme or insatiable desire for wealth or gain". This exactly parallels the phrase in the question. Therefore, Option A is fully consistent with standard usage and meaning.

Why Other Options Are Wrong:
Option B, "Actuary", refers to a professional who analyses financial risk, especially in insurance; it is a job title, not a moral quality. Option C, "Antiquary", is a person who studies or collects antiques and old objects, unrelated to greed for wealth as such. Option D, "Apostate", is someone who abandons a religious or political belief. None of these concepts describe insatiable greed for riches, so they cannot be correct here.

Common Pitfalls:
Because all the options begin with the letter "A", some candidates try to guess based on sound or vague familiarity. Another common error is confusing "avarice" with "average" or "avaricious" without knowing the root meaning. To avoid such confusion, always break the phrase in the stem into key ideas and match them carefully with dictionary meanings. Memorising common one-word substitutions like "avarice", "altruism", and "agnostic" will also help significantly in vocabulary sections.

Final Answer:
The correct answer is "Avarice".