In the following English vocabulary question, you are given a short descriptive phrase. Choose, from the four alternatives, the one word that best substitutes the phrase "fear of pain".

Introduction / Context:
This is a one word substitution question from English vocabulary based on Greek roots used for different phobias. The phrase given is fear of pain. You have to identify which option correctly names this particular phobia. Such questions are common in competitive exams and help test how well you know specialised vocabulary built from classical roots.

Given Data / Assumptions:

• The descriptive phrase is fear of pain.
• Option A: Mysophobia.
• Option B: Algophobia.
• Option C: Acrophobia.
• Option D: Homophobia.
• We assume that the options are standard English words formed from Greek roots, each referring to a different fear.

Concept / Approach:
Many English words for phobias are based on Greek. The suffix phobia means irrational fear of something. The key is to know or recall what each prefix stands for. The Greek root algo or algos relates to pain. Therefore, algophobia is the technical term for fear of pain. Myso refers to dirt or contamination, acro refers to heights, and homo here refers to same, used in the social context of homosexuality. Matching these roots with the phrase fear of pain leads to the correct choice.

Step-by-Step Solution:
Step 1: Break down each option into its root and the suffix phobia. For example, algophobia is algo plus phobia.Step 2: Recall that algo is related to pain, as seen in words like analgesic, a medicine that removes pain.Step 3: Conclude that algophobia literally means fear of pain, which matches the phrase exactly.Step 4: Examine mysophobia. Myso is associated with dirt or contamination; mysophobia means fear of dirt or germs, not pain.Step 5: Look at acrophobia; acro refers to heights, so acrophobia is fear of heights. Homophobia refers to irrational fear or dislike of homosexuality. None of these fits fear of pain, so only algophobia is correct.

Verification / Alternative check:
To verify, test the words in example sentences. A person with algophobia may avoid any situation that could cause physical pain, such as medical procedures. A person with mysophobia might constantly wash hands due to fear of germs. Someone with acrophobia will avoid high places like tall buildings or bridges. Homophobia relates to negative attitudes towards homosexual people. Only the first example directly involves fear of pain, confirming that algophobia is the correct one word substitution for the phrase in the stem.

Why Other Options Are Wrong:
Mysophobia is incorrectly linked to pain if chosen. It specifically deals with fear of contamination, dirt, or germs. Acrophobia is limited to fear of heights and has no connection to pain as such, even though falling from a height might cause pain in real life. Homophobia is a social and psychological term related to prejudice towards homosexual people and is not used to describe a medical fear of pain. None of these options directly expresses fear of pain.

Common Pitfalls:
A major challenge with one word substitution questions on phobias is that learners may only be familiar with a few common ones like acrophobia or claustrophobia and then guess based on partial memory. Another trap is to focus only on the familiar sounding part of the word without analysing the root. A good exam strategy is to systematically learn the most frequent roots such as acro, mys, agor, and algo so that you can quickly decode new phobia words during the test.

Final Answer:
The one word that best substitutes the phrase fear of pain is Algophobia, so option B is correct.