Choose the one-word substitute for the expression "A person who lays too much stress on bookish learning".

Introduction / Context:
This question is about one-word substitution, a favourite topic in many English exams. You are given a descriptive phrase and asked to choose a single word that captures its meaning. The phrase here describes a person who focuses excessively on bookish learning and minor details rather than practical understanding or broader wisdom.

Given Data / Assumptions:

• The description is "A person who lays too much stress on bookish learning".
• The options are "Pervert", "Pedant", "Philosopher", and "Scholar".
• We assume standard dictionary meanings and common exam usage.
• Only one option exactly matches the given description.

Concept / Approach:
The crucial idea in the phrase is "too much stress on bookish learning". It suggests excess, narrowness, and obsession with details or rules. In English, "pedant" is the word used for someone who shows off learning and is overly concerned with formal rules and minor points of knowledge. We must therefore identify that among the choices and eliminate words that suggest different qualities.

Step-by-Step Solution:
Step 1: Examine "Pedant". A pedant is someone who makes an excessive display of learning or is unreasonably concerned with accuracy and formality, often focusing on trivial details.Step 2: Compare that with the phrase in the question. Both emphasise "too much" or excessive stress on learning from books and rules.Step 3: Examine "Scholar". A scholar is simply a learned person. The word does not carry the negative idea of excessive or narrow concern with book knowledge.Step 4: Examine "Philosopher". A philosopher is someone who studies or reflects on fundamental questions of existence, knowledge, and ethics, not someone necessarily obsessed with bookish details.Step 5: Examine "Pervert". This usually refers to a person with abnormal or unacceptable behaviour, especially in a moral or social sense; it is unrelated to the idea of bookishness.Step 6: Since only "Pedant" fits the idea of excessive bookish learning, it is the correct answer.

Verification / Alternative check:
Look at typical sentences: "He is a real pedant who corrects everyone's grammar in conversation" and "Her pedantic attitude makes discussions tiring". In both cases, the people are not praised for broad wisdom but criticised for narrow, overly academic focus. The phrase in the question similarly criticises overemphasis on book learning, which confirms the match with "pedant".

Why Other Options Are Wrong:
Option A, "Pervert", is entirely unrelated and generally refers to socially or morally deviant behaviour.
Option C, "Philosopher", has a more noble meaning and suggests deep thought, not narrow bookishness.
Option D, "Scholar", is neutral or positive, indicating learning but not excessive or showy attachment to it.

Common Pitfalls:
Students sometimes confuse "scholar" and "pedant" because both relate to learning. However, the phrase "too much stress on bookish learning" clearly introduces a negative evaluation, which points towards "pedant" rather than "scholar". Another pitfall is guessing from partial familiarity with the word without recalling its exact nuance.

Final Answer:
The correct one-word substitute is "Pedant", so option B is correct.