This one word substitution question asks you to select the most appropriate term for the given description: Chief of a group of workmen.

Introduction / Context:
One word substitution questions measure your vocabulary and your familiarity with specific technical or occupational terms. Here, the description Chief of a group of workmen refers to a person who directly supervises labourers or workers, especially in factories, construction sites, or workshops. The aim is to find the term used in industrial and labour contexts for such a supervisor.

Given Data / Assumptions:

• The phrase describes a leader or supervisor of workmen.
• The setting is likely industrial, mechanical, or construction related.
• Options are chieftain, engineer, foreman, and middleman.
• We assume standard modern English usage in business and engineering environments.

Concept / Approach:
In factories, construction sites, and similar workplaces, the term foreman is used for the person in charge of a group of workers. The foreman supervises tasks, ensures safety, and reports to higher management. Chieftain usually describes the head of a tribe or clan, not industrial workers. Engineer is a professional who designs, plans, or maintains systems, but is not defined specifically as chief of workmen. A middleman is an intermediary in trade or business transactions, not a supervisor on a work site.

Step-by-Step Solution:
Step 1: Interpret the phrase group of workmen as industrial or manual workers. Step 2: Recall the common job title for the leader who directly supervises such workers, which is foreman. Step 3: Examine option c, foreman, and note that dictionaries define it as a worker who supervises and directs other workers. Step 4: Consider chieftain, which is mostly used in historical or tribal contexts and does not match modern industrial workplaces. Step 5: Consider engineer, which refers to a qualified professional involved in technical design or maintenance, not specifically the chief of a group of workmen. Step 6: Consider middleman, which is a person who acts as an intermediary in trade, making this option unrelated to supervising workmen. Step 7: Conclude that foreman is the only word that exactly matches the given description.

Verification / Alternative check:
Check usage in example sentences: The foreman assigned tasks to each worker on the site or The factory foreman ensures that the production line runs smoothly. These clearly refer to a supervisor of workmen. No one would use chieftain, engineer, or middleman in such contexts. This verifies that foreman is the correct one word substitution.

Why Other Options Are Wrong:
Chieftain is wrong because it is associated with tribes, clans, and traditional leadership, not modern work groups. Engineer is wrong because it describes a professional occupation that can exist without supervising workmen and does not specifically mean chief of workers. Middleman is wrong as it refers to an agent between producer and consumer in trade, completely different from supervising workers on a job site.

Common Pitfalls:
Learners sometimes choose engineer because they associate engineering sites with workmen, but the definition in the question focuses on direct supervision, not on technical qualification. Others may choose chieftain due to the word chief, but ignoring the tribal context. Always match the exact setting and description rather than picking a word that only partly overlaps in meaning.

Final Answer:
The correct one word substitution for Chief of a group of workmen is foreman.