In the following question, select the one word that best substitutes the given phrase: “A person who lives by himself.”

Introduction / Context:
This question tests your knowledge of one word substitutions for descriptions of people. The phrase provided is “a person who lives by himself.” Many competitive exams include such items to check whether you know concise words for social roles and personality types. The correct term here must refer to someone who deliberately lives in seclusion away from social life.

Given Data / Assumptions:

• The phrase describes a person who lives alone and is socially withdrawn or isolated.
• Recluse means a person who lives a solitary life and tends to avoid other people.
• Bemuse means to confuse or puzzle someone, and is a verb, not a noun describing a person type.
• Applause refers to clapping or approval from an audience, not a kind of person.
• Abstruse means difficult to understand, describing ideas, not people who live alone.
• The answer must be a noun that directly refers to a solitary person.

Concept / Approach:
For one word substitution questions, focus on the core concept in the phrase. Here the concept is a person who lives alone as a way of life. Words like bachelor or widower describe marital status, while recluse describes a person who chooses seclusion. The distractor options are either other parts of speech or unrelated nouns. By checking the part of speech and meaning of each option, we can quickly eliminate those that cannot substitute the phrase in a sentence without changing grammar or meaning.

Step-by-Step Solution:
Step 1: Interpret the phrase. It implies not simply living alone by chance, but a more general idea of a solitary person. Step 2: Examine Recluse. This word is defined as a person who lives a solitary life and avoids the company of others. This fits closely with the idea of living by himself in a withdrawn manner. Step 3: Consider Bemuse. This is a verb meaning to bewilder or confuse someone. It cannot replace a noun phrase like “a person who lives by himself.” Step 4: Consider Applause. This noun refers to public clapping or praise after a performance. It does not describe a person. Step 5: Consider Abstruse. This adjective describes something that is difficult to understand, such as an abstruse theory. It is not a label for a person type. Step 6: Since only Recluse describes a person who lives in solitude, it is the correct answer.

Verification / Alternative check:
Try substituting each option into a sentence. “He is a recluse who rarely leaves his house” makes sense and matches the phrase exactly. Using Bemuse, Applause or Abstruse in the same sentence would fail grammatically or semantically. Standard dictionaries also define recluse as a solitary person who avoids social contact, confirming that it is the best one word substitute for the phrase given.

Why Other Options Are Wrong:
Bemuse is a verb, not a noun, and refers to confusing someone. Applause is an action by a crowd, not an individual life style. Abstruse modifies abstract concepts, not social habits. None of these options carries the idea of a person living alone by choice. Consequently, choosing any of them would result in grammatically incorrect or meaningless sentences when substituted for the phrase.

Common Pitfalls:
Some students may be unfamiliar with the word Recluse and feel tempted by options that simply sound complex. Others may not pay attention to part of speech and mistakenly select adjectives or verbs in place of required nouns. To avoid such errors, build a small mental bank of words that describe personal roles and habits, such as recluse, extrovert, introvert and connoisseur, and always test whether the candidate word can grammatically replace the phrase as it appears in the sentence.

Final Answer:
The correct one word substitute for “a person who lives by himself” is Recluse, so the correct answer is option Recluse.