Out of the four alternatives, choose the one word which can be substituted for the given description. One who will do any job for anyone for money.

Introduction:
One word substitution questions often focus on words describing types of people. The description here refers to someone who is driven mainly by money and who is willing to work for anyone, without loyalty or moral concern. This idea is captured by the word "mercenary".

Given Data / Assumptions:
- Description: "One who will do any job for anyone for money."
- Options: Mercenary, Recruit, Hoodlum, Merchant.
- We assume the emphasis is on willingness to work purely for payment, without regard to principle or loyalty.

Concept / Approach:
The word "mercenary" originally referred to soldiers hired to fight for any country that paid them, rather than for patriotism. More broadly, it now describes anyone whose actions are motivated mainly by money, often with a negative suggestion that they lack loyalty or morals. The correct answer must reflect this idea, not just any person connected with work or business.

Step-by-Step Solution:
Step 1: Recall that "mercenary" can be used both as a noun (a hired soldier) and as an adjective (motivated only by money).Step 2: Check how closely this matches the description of a person who will do any job for anyone for money.Step 3: Examine "recruit". A recruit is someone who has recently joined an organisation, especially the armed forces; it does not imply greed.Step 4: Examine "hoodlum". This refers to a violent or criminal person, but not necessarily one who works for anyone purely for money.Step 5: Examine "merchant". This is a trader or shop owner engaged in buying and selling goods, not simply someone who will work for whoever pays. Therefore "mercenary" is the best fit.

Verification / Alternative check:
Use each word in a sentence. "He is a mercenary who fights for the highest bidder" matches the idea perfectly. "He is a recruit" describes a new member, not a money driven worker. "He is a hoodlum" describes a criminal, and "He is a merchant" describes a businessperson. Only "mercenary" conveys the idea of doing any job for anyone purely for payment.

Why Other Options Are Wrong:
Option B, Recruit, focuses on someone who has newly joined a group or army and does not imply greed. Option C, Hoodlum, implies criminal behaviour but not necessarily money motivation in a neutral job sense. Option D, Merchant, refers to a trader, which is a specific legal occupation and not by itself morally questionable. Only option A, Mercenary, directly aligns with the description of a person who acts purely for money and can be hired by anyone.

Common Pitfalls:
Some candidates may confuse "mercenary" with "merchant" because both start with "mer", or they may choose "hoodlum" because they associate doing "any job" with criminal acts. However, the description does not say the job is illegal; it only says the person will work for anyone for money. Remember that "mercenary" carries a strong nuance of acting purely for payment, often without principle.

Final Answer:
The correct one word substitute is Mercenary.